The database of episodic adventures for it is quite lengthy, counting only the commercial ones, at over 30. Adding the magazine ones pushes it well over 50.
Classic Traveller (CT) alone had 13 published non-campaign adventures (Adv 1 to 13), 7 double-adventure books with 2 each, (DA 1 to DA 7), 3 campaign adventures† (TTA, Tarsus, Beltstrike), 2 campaign frameworks‡ (Spinward Marches Campaign and Adv 0), 76 semi-detailed adventure seeds (76 patrons), 24 issues of JTAS at 1-3 short adventures apiece. (Note that CT is actually 2 editions: pre 1981 and post 1981, but the adventures and such are the same.)
Adding MegaTraveller's list, there are fewer: a dozen or so from Challenge Magazine, plus two campaign modules (Knightfall and Arrival Vengeance).
There are several dozen more third party adventures for CT.
Further, all the above can easily be run in the current edition, Mongoose's Traveller, with only minor modifications.
Acquiring the vast majority of the above mentioned is done relatively inexpensively.
- The CT CD-ROM is available for $35 from Far Future Enterprises, and includes in PDF all the CT rulebooks, including Books 0-8, Adv 0-13, Supplements 1-12, DA 1-7, AM 1-8, The Traveller Book, Starter Traveller, The Traveller Adventure, Spinward Marches Campaign, Tarsus, Beltstrike, and Striker, plus several board games, and 1st Editions of Books 1-3 & 5.
- The JTAS CD-Rom includes all the JTAS issues, plus all the CT issues from Challenge magazine. Also $35.
- The Apocrypha and Apocrypha 2 CD's add several dozen more. These are 3rd party expansions for CT, including adventures, expansion rules, alternate settings. $35 each.
- The MegaTraveller CD-ROM includes all the GDW released material for MegaTraveller. Sadly, it doesn't include the quite excellent DGP materials. It also includes the MT specific Challenge articles. Note that this is a much better ruleset than CT for many people. Also $35.
Note that the current ruleeset, Mongoose Traveller, has its own adventures; 1-2 short ones in every product, plus a 12-episode campaign free in PDF, plus an average of 1 adventure per issue since the mid 80's in their free house magazine, Skills and Portents While not exactly compatible with CT, the mechanics are close enough that the specific mechanics in CT adventures won't raise too many eyebrows, and character conversion is a matter of knowing which skills don't exist or are renamed in which edition, and accounting for those changes. The core book is $40, the adventures in S&P and the campaign are free PDF, and the corebook PDF is about $25... 760 patrons is quite usable as well, providing adventure seeds galore... 760 of them.
Also, there are a surprising number of fan-written adventures on the net. Well, not so surprising, given that the game-line's history starts in 1977... but still.
† the campaign advetures are quite easily broken apart and used as chunks episodically. Tarsus and Beltstrike both contain 5 episode mini-campaigns, plus a lot of ideas for further work in both settings. They were pricy at $20 in the mid 1980s... but as part of the CD, dirt cheap.
‡ These campaign frameworks won't meet your needs. They are setups with a couple of adventure seeds, and large meta-plot issues being covered. They provide a clear way to set-up and run a low-prep improvised campaign.