Getting into Classic Traveller in 202X
Someone told you that Traveller is a cool SF TTRPG, and you heard that Classic Traveller (CT) is a good version of it. So, how do you start? This was a (relatively) brief guide that I wrote in August/September 2023, with some edits in December. This is a more permanent home for it than a PDF uploaded to various discords.
Contents
- Choosing a Core Book
- Additional Books and Supplements
- A note about those letters
- Core Mechanics
- Character Generation
- What do players do?
- Getting a Sector
- Additional Resources
Choosing a Core Book
First of all, there are a few different versions to choose from:
- Box Sets: CT had two different editions of the deluxe box set, one published in 1977 and one in 1981.
- 1977: The original edition, containing three Little Black Books (LBBs) in digest size.
- Book 1 - Characters and Combat
- Book 2 - Starships
- Book 3 - Worlds and Adventures
- 1981: A second edition that has some cleaned up rules following the 1977 box set, but the same LBBs. This is a fairly easy edition to obtain. There are a couple of notable changes from 1977:
- Weapon damage is whole multiples of d6, rather than the d6± values of 77.
- Trade routes become X-Boat routes, which are tied to the Third Imperium (3I) setting.
- Starter Traveller from 1983 is a somewhat simplified version of CT81. Notably, it uses range-bands for space combat, compared to 2D vector combat in most other versions.
- 1977: The original edition, containing three Little Black Books (LBBs) in digest size.
- All-in Books:
- The Traveller Book: This is a larger page (letter?) compared to the digest books in the box sets. This lets things like tables be slightly nicer to reference, because they are less cramped. There is also more art. This combines all three of the books in the 1981 box set into one book. There are a handful of rules that are new to this.
- Facsimile Edition: A combination of the LBBs from the 1981 box set into one file/book, with a good amount of errata. At the time of writing, available for free on DriveThruRPG.
Pretty much, you can choose any of the above and it will be fine. The cheapest and quickest way in is with the Facsimile Edition, which also has fairly extensive errata. The Traveller Book (TTB) is also a solid option, and is available as a print-on-demand book. All of them are available on a disc (or USB drive) from Marc Miller at https://www.farfuture.net/ should you want to choose from all of them. I use TTB, if that has any bearing on your decision.
Additional Books and Supplements
In addition to the core books, there are a number of published supplements that may or may not be of interest to you as a Traveller referee. All of these are definitely optional; you only need one of the options from above for as much play as you like.
Books
First, we have the extra books. These provide more detailed careers and rules for the existing careers, subsystems around those careers, different ship building rules (including for bigger ships), and robots. In general, these expanded careers should not be used with the original ones because they have a tendency to give many more skills. You could consider these as superseding or extending the books mentioned above, potentially.
Some of these books (B4 and B5) were published before the 1981 box set, although they are compatible regardless; if you find a good deal for something that you want, it will be useable with either version.
- Mercenary (Book 4) - details for running a mercenary company. It also includes new weapons and equipment. It has more detailed rules for character generation, with a roll each year.
- High Guard (Book 5) - details for space navy games. Has a new ship-building system that tends to lead to bigger ships - often one that people ignore for the Book 2 ship rules instead.
- Scouts (Book 6 ) - details for the Scout career, with more complex character generation a la Book 4, as well as extended system generation. This is one of the first books that really assumes the Third Imperium (3I) as a default.
- Merchant Prince (Book 7) - expanded Merchant career. It also covers trading houses and has more detailed trade rules.
- Robots (Book 8) - How to make/build robot characters. Expands on and changes on robot rules first supplied in the Journal of the Traveller’s Aid Society (JTAS). Also includes how they work within the 3I.
Book 5 is possibly one of the most discussed amongst CT fans, since it changes the style of ships from the LBBs, in particular by making it possible to have them be much bigger. If you are someone who likes a small-ship setting where something weighing 5000 dTons is the biggest thing around, then avoid the new rules in B5. Additionally, from B6 onwards the books are more tied to the 3I. The links to the 3I setting are generally easy to ignore or replace, but it is worth noting.
Supplements
In addition to the books, there are a number of supplements. These are more focused on a single thing. While there are a fair few of these, a few stand out as worth grabbing and are often recommended:
- Citizens of the Imperium (S4): this one is usually thrown into the mix by many referees looking for some more varied Travellers. It has additional careers, including things like scientists, air force, hunters. Well worth considering as an expansion of the Other career in the LBBs.
- 76 Patrons (S6): 76 situations to throw your players into. These function as little adventure seeds that can be useful for an emergency.
Most of the other supplements are a little more situational. S3 (The Spinward Marches) and S10 (The Solomani Rim) are premade sectors that you could use if you want to not roll up your own. You could also use specific planets from either sector if you wanted to. S5, S7, and S9 (Lightning Class Cruisers, Traders and Gunboats, and Fighting Ships) are new ship designs and might be useful if you want those. S8 and S11 (Library Data) are glossaries and definitions of various terms, often linked to the Third Imperium/Charted Space. S1 (1001 Characters) and S13 (Veterans) are additional NPCs (S1 with the original ruleset, S13 focusing on hireable mercenaries using Book 4 rules).
Other
There are also the Alien Modules, should you want pre-made alien races, and various adventures, which might or might not be to your liking. One book here is worth calling out specially though, and that is The Traveller Adventure, which includes some suggestions for how to evaluate skills and when to call for rolls and similar, which might be of interest.
A good overview of the official publications for CT from Game Design Workshop can be found on the Far Futures Website. There are also numerous third party products that I am not going into here, but the Far Future website has details on many of those as well.
Conclusion
We will now have selected a core set of books, and might have added some extra books or supplements. I would recommend that, in general, you start with just Books 1-3, optionally adding S4 for some different careers (if desired) and then whatever makes the most sense for the game that you want to run.
A note about those letters
If you are looking at Traveller things (not just Classic, but in all sorts of derived systems) you will often see strings of letters and numbers being mixed. For example, character stats are traditionally written on one line, like AA7758
.
If a value is 10 or more, letters are used, with 10 = A, 11 = B, 12 = C, all the way to 15 = F. CT tends to stop here, but other editions may go further. This means that it is unambiguous which value refers to which stat: 7B23A5
is less likely to confuse than 71123105
, where it is not clear if this is 7B21
or 71C1
or 71D
.
Such hex numbers are most prominent in character stats and the Universal World Profile that describes the important stats of a planet.
Of course, if you prefer to write this differently for yourself, feel free, but you will see the single-line, hex notation for many Traveller publications, not just CT, so as someone running Traveller it is good to understand the convention.
Core Mechanics
The books explain roughly what the setting looks like, but we will come back to that. For now we will think about how the core game mechanics (might) work.
An important thing to consider is that CT does not have a unified system like many games, especailly newer ones. Each skill is potentially treated differently, so make sure that you spend some time looking over the suggestions of how they are used. The core books have examples attached to all the skills, some of which are more concrete that others. This leads to a rather freeform system, with the referee adjudicating things on an ad hoc, case-by-case basis. In addition, Dice Modifiers (DMs) do not need to be the value of the skill (that is, just because you have medical-3 it does not follow that you get +3 to all medical rolls). If something is difficult to do, maybe the skill just makes it possible to try and only exceptional skill gives you a bonus to that attempt?
An example might be something like trauma surgery - if you do not have medical-3 you can not do effective surgery at all, but medical-5 will get you a +1 DM because you are one of the best surgeons available.
To get an understanding of how a game of Traveller without a unified central mechanic might work, the series of posts by Chris Kubasik from Tales to Astound is super worth a read: https://talestoastound.wordpress.com/traveller-out-of-the-box/
If you want a system with a unified mechanic, a common approach is to set some target numbers. Rule 68A (that is target numbers of 6, 8, 10 for easy, normal, difficult tasks) is a widely used approach. I have also seen 8AC (8, 10, 12) proposed for a harsher system that expects Dice Modifiers. MegaTraveller is a development of CT that also has a universal mechanic behind task rolls and is very compatible with CT, so it could also be used. All of this really depends on what clicks for you, and if you like a hands-off, ad hoc approach or not.
Character Generation
This is well-explained in the book, for the most part. One thing to note is that death in character creation is called out as an optional thing in every book but the 1977 box set. Making Travellers just end chargen and moving into play is completely valid.
In addition, while the books only allow for one career, this is an easy houerule if you want to have Travellers be a little more level - having a retired admiral with a huge amount of skills in the same freetrading crew as a marine who washed out after a single term can be a little disappointing for some players. You can just allow a PC who crashed out of a career to try and enlist in another. Having something akin to Mongoose Traveller’s ‘Drifter’ career might be worthwhile if no other service will take them.
A common suggestion is to allow for a couple of rerolls during character generation. In general, CT is pretty harsh on creating Travellers, so it is a nice bit of buffer.
Another very nice rule is to let a player roll for skills first, and then choose the table to get the improvement from. Again, this gives players a little more control over their PC, while still leaving a lot up to random chance.
Should you want additional careers, they are not too complex to make by using the existing ones as models. S4 is also worth a look if you want Travellers who are not all miltary veterans of some kind.
If a campaign is going to need certain skills, consider putting them up for grabs from various players. Getting pilot is rather rare if you look at the tables, for example, so you might want to consider letting a PC have it. Perhaps that is in exchange for something else, whether that is an in-game problem like an enemy or simply a different skill.
What do players do?
We depart here from things like publishing dates and solid advice for the higher pastures of good-natured suggestions. Traveller is jokingly referred to as a spreadsheet-based game about people having a midlife crisis in a spaceship. This is not entirely wrong, but games can certainly be more than that.
The Ship
One important consideration is whether to have the Travellers own or access a ship at all. There are certainly ways to run a campaign that does not presuppose that Travellers are shipowners, of which the following two are the most obvious:
- Single planet campaigns certainly work, although these are a bit light on actual travelling. This has the benefit of letting Travellers really dive into a strange society and get used to it. This is probably the least common kind of campaign, but it can certainly be a strong start, with ‘get off this planet’ as a solid beginning goal.
- Travelling factors/traders. Here, the Travellers will engage in trade and troubleshooting on a planet, and then move on by buying (or working) passage to another planet. They may have a few tons of goods to trade, or they may be taking on jobs that entail that travel. This can be thought of as a street-level campaign. Without a ship a number of options are off the table, leaving the Traveller with nothing but what they can carry. This is a very strong option for a solo game or with only a couple of players.
If the Travellers are going to have a ship, then the next obvious question is what type of ship to give them.
A scout ship is a good option, and within the 3I setting comes with built-in plot hooks; the ship belongs to the Imperial Scout Service, and can be commandered whenever needed. It can only carry a very minimal cargo, however. Freetraders are less susceptible to being commandeered, and with their larger cargo capacity are more likely to make a profit from trading, which is why they usually come with the loan as the hook instead. Other ship types may be more or less useful. You could always make a new one. The standard Far Trader is roughly 200dTons, with a J2 drive. This can obviously be varied, but is a good standard: there is still plenty of room to grow into bigger vessels, while being capable and not too expensive.
Which leads to the next points: if the Travellers are to be given a ship, how have they paid for it? If they have a patron, they might be given the use of it without needing to actually pay for it. This obviously makes them beholden to that patron. For some campaigns this might be the entire framing device: the Travellers are troubleshooters for a large corporation or a noble house, or maybe they are still in Imperial service as spies masquerading as normal free traders. Consequently, they travel where they are told to, possibly with some downtime for their own shenanigens and schemes between mandated missions.
Most campaigns will have Travellers as unattached free agents. If they do not own the ship, then they will need to pay for it somehow. The default assumption is that the ship requires a loan to be repaid. This requires players who are interested in tracking profit from trade and for where to get the best deals for their current cargo. This is the classic CT campaign, and has the beats outlined in Book 2: travel through jumpspace for a week, land on a planet and spend a week selling cargo, finding passengers, getting a new cargo, whatever other trouble turns up, and then lighting out for the next one. This cycle then repeats. For this to be viable in the long-term, the Travellers need to make half of their loan repayment, plus fuel, living expenses, salaries, maintainence, and so on for every jump, on average. That may mean that they need to take dangerous jobs, so you have built-in hooks here: the Travellers need money, so anything that gets them money should at least get their attention. Sensible Travellers with a loan will not often be doing jobs out of charity, and low-paying jobs are not going to attract them. They need to think big, and get paid accordingly.
Some players are less interested in such spreadsheeting and tracking though and just want to ply the spacelanes causing trouble in bars. There is nothing wrong with simply giving the Travellers a ship. In one interesting respect, it might even be easier: the scale of ship repayments simply dwarfs almost all personal items. That means that if you want a more Firefly-esque experience of hard-scrabble drifters who are barely getting by, it might be possible to just give them the ship outright. They will still need to cover maintainence and fuel and salaries, but those are much more reasonable expenses, and a ship can skate by without them for a while. At this scale, jobs taken can pay much less. Normally, the Travellers will be needing 154 500 credits a month for loan repayments on a Free Trader, plus 37 080 credits for maintainence, plus life support, fuel and any salaries. If they own the ship, they only need the 40 000 to 50 000 credits a month for maintainence, life support, fuel, and similar expenses. Doing a few small jobs or hauling only a few dTons of cargo now becomes much more feasible, as does staying in one system for longer, if you want to delve into local-scale politics and drama.
That said, the tight cycle of the loan repayment requirement driving jobs and adventures is certainly an engine for building adventures. For an insight into how it drives things and why you might want to keep the loan repayments as a core driver of the game, this blog post by Sir Poley is a good read: https://sirpoley.tumblr.com/post/623913566725193728/on-the-four-table-legs-of-traveller-leg (The rest of the series is also good, but this is the salient one for this section).
Patrons and NPCs
These are very easy for a referee to invent on the fly. Average stats are 7 for everything, so if someone is meant to be very educated or strong, just bump that up as needed: 7777A7, 977777. Give them a couple of relevant skills, maybe some equipment or assets, and you are done. NPCs fit on a few lines of text:
- Lady Katrina Donahugh Age: 47
- 69777B
- Blade Cbt (Foil)-1, Admin-3, Leader-2
- Expensive clothes, well-used rapier, servants at her beck and call, fancy house in the nice part of town
- Jaime Laumer Age: 34
- 589485
- Mechanic-2, Vacc Suit-1, Electronics-1
- Battered vacc suit, reliable toolbox, diagnostic kit, union membership
Add a note about what they want and you are off to the races (the One-Roll NPC and One-Roll Patron tables in Stars Without Number are good for inspiration, and are available in the free version).
Traveller is an inherently socially-focused game: there is little money to be made in systems with no people, at least unless you can make a massive payout from whatever you find there. Even pirates need victims and will be drawn towards inhabited systems. More commonly than spending time in the vast uncharted wildernesses, Travellers will be meeting local business owners, factors from large trading houses, customs agents, pirates, local government officials, other Travellers, paying passengers, Imperial spies, weird alien diplomats…. There is a reason that Supplement 1 was 1001 Characters.
It is worth thinking about how Travellers are viewed by your NPCs. What can the Travellers do for them that the NPC is willing to pay for? Especially if the Travellers need to raise hundreds of thousands of credits a month, this is a good opportunity to get them involved in local schemes and bad decisions. If they have a spaceship, they can (almost) always just run away from the problems this might cause, although leaving a planet should not always leave consequences behind as well. Depending on what the problems are, or who was inconvenienced, other people can travel to different systems if they really want to.
Having Travellers loop back onto a planet and meet the same people they did last time, deepening links to friends and making for recurring enemies, is also well-worth encouraging. Getting a job from a friend is more appealing: you know that you can trust them. Likewise, a job that harms an enemy in some way is also more appealing than one that harms an enemy, other rewards all being equivalent. These friends and enemies can also be corporations, navies and similar organisations: The Traveller Adventure for example has numerous sections focusing on a trade war between the Tukera and Oberlindes corporations.
Travel
The week-long jump and no FTL communications is an important part of the CT setting: Travellers are isolated, even if they are reporting to someone. When a single message takes a minimum of two weeks for a reply (one jump out, one jump back), then tight control over subordinates is not possible. Everyone needs to delegate things to people that they trust and empower them to act on their own initiative.
This means that Travellers will have to take control of their own situations; no one else is going to. It also ties back into NPCs and patrons: showing that they are sensible and capable of independent action should be likely to get the Travellers more lucrative job offers and advancement. Once they have done a few jobs and are known to be reliable, they might also be recommended to friends of the patron. Again, recurring patron NPCs and organisations make this work even better.
It is also worth remembering that Travelling can also be done without owning a ship: working passage or paying for passage on a ship going where you want to go is an option. The more remote the place that you are trying to get to, the more likely that you will need to outright charter a ship instead of just taking passage. A sensible cost for this would be to cover the loan repayment, salaries, fuel and maintainence for the time that the ship is needed for, plus a bit extra.
Implications for Bounty Hunting
The way that travel works by default: week-long jumps and no easy way to see where a ship has gone once it jumps means that the ’travelling bounty hunter’ archetype is not easily sustainable. You have no easy way to know where to go without hitting the ground and asking, so the number of possibilities for where a given ship has jumped to rapidly balloons out of control, assuming that a target is trying to keep moving rapidly.
The sensible thing to do as a bounty hunter is to remain in one well-trafficked system and have contacts with various border patrols and customs agents, and an updated list of persons of interest. When a POI trips your network, then go and grab them. This might work best as an opportunistic career, with the hunter normally doing something else and taking bounties when they become available.
For extremely high value targets, especially if the ship loan costs are borne by someone else, it might make sense to try and hunt them actively, but trying to track someone who is trying to remain hidden is going to be very difficult. It is one thing to ask around and get the next port of call for someone, but if they lie or change ships at the last moment they will be very difficult for a given individual to track compared to a network of hunters who sit in their own system and then extradite captured bounties.
Adventures
The range of adventures for Travellers can be pretty wide - you have multiple planets in a subsector, each of which can have its own problems - but in general, for a long campaign having some variety is good. Having a campaign that only ever does sneaky heists on rich nobles using a Free Trader as a cover story will become monotonous after a while: throw them into local politics; have the planet erupt into open warfare; have pirates attacking the Highport causing traffic to be locked down just before they need to make their escape; this planet has incredibly hostile native life and the power plant powering the defensive perimeter is failing due to lack of maintainence and parts.
If you are looking for ideas, stealing from old stories works well. These can be from age of sail and exploration stories - Hornblower, Aubrey/Maturin, Flashman, H Rider Haggard - in addition to the various old-school SF that inspired Traveller - Dumarest of Terra, H. Beam Piper, the Dorsai books, Laumer’s Retief books, Hammer’s Slammers. Various historical events can work as well, especially during the aforementioned age of sail, but even modern events can provide useful brain fodder for hooks with a bit of thought.
For more purpose-made adventure seeds, Supplement 6 (76 Patrons) is worth a look. There are a fair number of fan-made adventures available on various websites (see the Resources section later). Official adventures are also available. One really nice thing about Traveller is that the various editions are pretty compatible - CT, MegaTraveller, Traveller: The New Era, Mongoose Traveller (either version), various things for Cepheus Engine, all work with pretty much no conversion (unless there are special ships). Some do presuppose aliens which may not exist in your setting, but they are usually not too difficult to work around. These full-fledged adventures will usually need less work and have more meat than 76’s offerings and some of the fan-made stuff, although they may not always fit into an ongoing campaign as well as the very lightly sketched suggestions.
The sandbox approach to campaigns works really well, if you can pull it off: build up networks of patrons (some of whom can be competing), keep coming back to the same systems to make them deeper and more real for players. Getting repeat jobs from old patrons and friends is nice. Changes from the activities of Travellers can also reflect: new leaders, new traders, destroyed space stations…. This will also mean that you do not need to develop a new planet from scratch every week, although that is also an entirely valid approach.
One suggestion I have is to avoid the ‘passenger is secretly a pirate hijacker’ cliché if you want your Travellers to keep taking passengers. Keeping passengers interesting but safe is a nice way to link them into the setting more. A better model (to my mind) is to have a passenger get into trouble either before or after leaving that the Travellers can get involved with. If they like a passenger, and a day after landing they get a message about the passenger being in trouble, that can kick off more varied adventures than getting the ship hijacked. Again. Likewise, a passenger that needs to get off the planet as soon as possible and needs to be protected until launch is a common literary trope.
Piracy
Piracy is a common thing for players to want to do, but in general should be approached carefully. A safe port is still needed for repairs, even if the ship has decided not to pay its loan back (skip-jumping). This definitely works best in a setting without strong local navies that can run anti-piracy patrols and similar.
Again, the restriction on communication speed means that messages about pirates will be delayed. If a pirate can jump out of a system before any organised response, they will likely get away. Repeated raiding will make that more difficult as the response ramps up.
If identified as pirates, a ship can probably expect short thrift, especially if they kill crew, not just steal cargo. Opportunistic piracy is more likely: an isolated ship that will not be able to report or similar soft targets as they come up, rather than a regular career.
Getting a Sector
Book 3 has rules for making sectors, including all the planets and such. There is value to doing this, but if it feels overwhelming, there are pre-made ones available. For CT specifically, S3 and S10 cover The Spinward Marches and the Solomani Rim which are each a complete sector. Other editions will have other sectors detailed.
When I say that the sector is detailed, this is still usually a very high-level overview. Depending on the sector it may have a few dozen systems, and most will get a few paragraphs of what makes them special at best, so you will need to flesh them out more fully if they become important to your campaign. This does mean that you can easily take a single system that you like from a totally different sector and put it in your new sector, if there is a published adventure set there that you like.
There are also numerous generators online that will make an entire sector or subsector with a button press, if you want something new and do not want to roll it up yourself. You will still need to do the work of figuring out how the planet actually works, mind you. If you need additional ideas, the world tags from Stars Without Number can also slot into a Traveller milieu, although the way planets are created is different.
One advantage of doing things manually is that you can consider each planet as you roll it up and think about what will be the reason Travellers might have to visit it. Robert Conley has a nice procedure that could be followed for this ( https://batintheattic.blogspot.com/2009/04/how-to-make-traveller-sandbox.html ) and is a pretty solid way of approaching it. The last point about simply choosing or making up the numbers for a UWP is worth remembering: the canon sectors do not match the distribution expected from purely random rolling, so there is no reason to feel bound by the rolls you make.
At the same time, you do not need to have details on everything in the sector to start play. You only need the details for the starting planet, and some rumours to link to a couple of nearby systems. Once the Travellers move towards the next system, you can build it up before they get there. I would suggest having the rough outline of the subsector in place: location of systems and the UWP for each. If you want to have multi-system polities, you can sketch out their borders, but do not feel pressured to do more than this: the important thing is to get going and have some dice hit the table, and waiting until you have a full sector or subsector fleshed out is just going to delay that. This is one reason that taking a pre-made sector can be useful, even if you then ignore whatever scant lore might exist for a given system in favour of what works for you.
As a leg up for those who want to steal an existing sector, here are some that I found interesting. For all of these, I looked at the high-level shape of polities for places that seemed to have conflict and potential. I have only looked at the sector, not the situation beyond it.
Unless you want to use the official 3I setting, I would suggest that you do not worry with the wiki links: just take the names and UWPs from the sector data and figure things out from there. You can also generate a nice poster map for each of these sectors (or subsectors) in a variety of styles using the Traveller Map tool.
- The Spinward Marches
- The Third Imperium faces off against the Zhodani Consulate across neutral territory.
- Wiki info
- Sector data
- Gateway
- Various small polities vie for supremacy. This could be a fun sector if you want the Travellers to build an empire, since there are no huge players here.
- Wiki info
- Sector data
- Mendan
- Various small polities that are slowly banding together into the Julian Confederation. This could be a great option for a more political campaign, either in support of the Confederation or opposing it.
- Wiki info
- Sector data
- Hinterworlds
- The Third Imperium have the smallest of toeholds in this sector, which otherwise has a number of smaller polities vying for dominance. Could be nice for 3I citizens who wish to get rich trading beyond the borders of the Imperium. Or perhaps they wish to be kings themselves?
- Wiki info
- Sector data
- Magyar
- The Third Imperium butts up against the Solomani Confederation. If you want a campaign in a sector with a border war looming (that goes hot during the campaign?) this is a good option.
- Wiki info
- Sector data
Additional Resources
CT has been around a long time, so there is plenty out there to look at, which is part of the confusion for how to start, I suppose. While the book has enough to get going with, the following are also worth checking out:
- The Traveller Wiki - a community edited wiki with details about systems, ships, details of publications. Lots of good stuff here.
- The Traveller Map - a great resource if you want to use the 3I setting. Information on planets, ways to handle routes between systems, different timelines. Easy to steal a sector from and use.
- It also has a tool for making nice maps of any given sector, or from a list of UWPs.
- Citizens of the Imperium - The official Traveller forum. Lots of good stuff here. If you find broken links from a blog or similar to it, then here is how to get a working one.
- Far Future Enterprises - Marc Miller’s company. A really good source of PDF compilations if you really fall down the rabbit hole.
- Traveller Discord - While I am sure others exist, this is the largest that I am aware of. Covers all versions of Traveller. The disboard link seems like it will let you join, but otherwise with the expiring invites I am not sure if there is a better one now.
- Freelance Traveller - long-running fanzine with a range of extra rules, reviews, adventures, equipment and so on.
- If you are looking for adventure seeds, the Getting off the ground section is worth perusing.
- Amber Zone - community-made adventures
- Zhodani Base - Good source of links to other things
- Section by Section Comparison - Google document detailing the differences between different versions of CT: 1977, 1981, The Traveller Book/Starter Traveller
- Traveller out of the box - A really solid series of blogposts about how to run CT in a light-weight, FKR-style way.
- The Four Legs of Traveller - a nice series of posts on what makes Traveller tick: ‘Finances, Character Creation, Patrons, and Random Encounters’.
There are numerous generators, both for characters and for sectors. I happen to like or have used the following, but plenty of others are out there. It is also a fun exercise to write your own.
- https://campaignwiki.org/traveller/edit A nice tool for making sectors. Can generate a map given a list of UWPs as well. Has versions for CT and Mongoose.
- https://ffilz.github.io/Gaming/travellercharacter.html CT Character Generator, optionally with S4 careers.