Actually, if you want the stuff Traveller was mostly derived from,
check out Poul Anderson's stuff (Baen has been re-issuing it).

A lot of trading stuff is there, as well as a lot of Navy stuff.

Baen is calling it The Technic Civilization Saga. the books are:
1 - The Van Rijn Method
2 - David Falkayn: Star Trader
3 - Rise of the Terran Empire
4 - Young Flandry
5 - Captain Flandry: Defender of the Terran Empire
6 - Sir Dominic Flandry: The Last Knight of Terra
7 - Flandry's Legacy

Also, much of andre Norton's Juveniles. Free Traxeres and First-In
Scouts derive from her books.

E. C Tubb's Dumarest books are where low berths and fast & slow drugs
come from.

Black Globes come from Pournelle's CoDminium stuff, and especially
from The Mote in God's Eye.

And A, Bertram Chandler's stuff has somewhat different tech than
Traveller, but a lot of good stuff. Again, Baen has all his Grimes
stories available.

Do note that one story is a crossover with Anderson's Flandry stuff.

And another has a really *nasty* species (slipped over from an
altenate universe, something that the stardrive in Chandler's stuff
makes all too easy).

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com