From my old website:
-Poul Anderson's space books. All of them. This includes the Flandry / Imperium cycle, the van Rijn/Falkayn/Polesotechnic League books, and the "incomplete" (but actually rather extensive) Psychotechnic League books. Not to mention some stand-alones like The Avatar, Tau Zero and Orion Shall Rise.
-Lois McMaster Bujold's Vorkosigan cycle, still growing.
-Elizabeth Moon's Hunting Party trilogy (Hunting Party, Flying Colors, and Winner's Circle), and several others set in the same universe.
-Robert Frezza's "McLendon's Syndrome" and its sequel "The VMR Theory."
-David Drake's "Hammer's Slammers" series, though just the first book will give you a good idea... Much of Drake's other work is readable in a Traveller context.
-Melissa Scott's Roads of Heaven trilogy. Variant (uses magic in space) but very Traveller feel besides this. She has also done some other things I recommend but can't remember the names of...
-Anne McCaffrey's Dinosaur Planet cycle, including "Death of Sleep", "Sassinak," "Dinosaur Planet," "Dinosaur Planet Survivors," and "Generation Warriors". Also read the Crystal Singer books and the Ship Who Sang cycle.
-Andre Norton's space books. This includes many pairs, trilogies and series as well as singles.
-Benford and Brin's "Heart of the Comet."
-Greg Bear's Eon trilogy, "Eon," "Eternity," and "Legacy." Legacy is the most Travelleresque of these, but they are all worth the read.
-David Brin's Earthclan books: Sundiver, Startide Rising, Uplift War, Brightness Reef, Infinity's Shore and Heaven's Reach.
-Brian Daley's Hobart Floyt trilogy: Requiem for a Ruler of Worlds, Jinx on a Terran Inheritance, and Fall of the White Ship Avatar. Sadly, Mr. Daley died a couple years ago, so we will never see more of this quintessentially Traveller series.
I did, however, just find a pair of posthumously published books: Gammalaw-Smoke on the Water, and Gammalaw-A Screaming Across the Sky. They are apparently the only finished parts of what was to be a much larger series. Gritty combat, gritty politics, good reading so far...
-Robert Heinlein's too-numerous-to-mention library of books. Highlights include "Starship Troopers," "StarBeast," and "Friday."
-Alfred Bester's "The Stars My Destination."
-Douglas Adams' Hitchhiker's Guide to the Galaxy trilogy, though only the first three are really worth it IMHO.
-Joe Haldeman's "Forever War." 'Nuf said.
-Frank Herbert's Dune series of books. While the later books pale before the original, all (by Frank) are worth reading.
-Joe Clifford Faust's Angel's Luck trilogy: Desperate Measures, Precious Cargo, and The Essence of Evil. I'll admit that the first book is a bit rough, but the other two are very good writing and very good reading.
-David Weber's Honor Harrington series, which is at six(?) books and growing.
-Arthur C. Clarke's "The Songs of Distant Earth" as well as the 2001 tetralogy and the Rama trilogy. Also worth the listen if you like Mike Oldfield (of "Tubular Bells" fame), is his "soundtrack" to "The Songs of Distant Earth".
-C.J. Cherryh's Chanur books, as well as the Downbelow Station/Cyteen/Forty Thousand in Gehenna cycle.
-Alan Dean Foster's Humanx Commonwealth stuff. All of it. This includes the Flinx books.
-E.C.Tubb's Dumarest of Terra cycle, last seen at over 20 books, but finally finished after 30 years (it started in 1967). This series is the inspiration for much of the flavor of travel-by-starship in Traveller.
-Larry Niven's Known Space stories, including the Ringworld books and the tales of Beowulf. Also look for the Smoke Ring books (Smoke Ring and The Integral Trees) and his collaboration with Pournelle and Barnes in Legacy of Heorot and Beowulf's Children.
-James Alan Gardner's Expendable, Vigilant, and Hunted. Scary universe for playing in, but wonderful toys and races.
-Jeffery D.Kooistra's Dykstra's War. There may be things in the Oort Cloud you didn't want to disturb...
-Larry Segriff's Alien Dreams. Good space Navy stuff. I haven't read the prequel (Spacer Dreams) yet, but I intend to.
-John DeChancie's StarRigger trilogy: Starrigger, Paradox Alley,and Redlimit Freeway. Better than all of his Castle <blank> series put together.
-Roger Zelazny's Lord of Light, Doorways in the Sand, and frankly anything else. Traveller related? No. Worth reading? No doubt.
-Massimiliano Frezzato's Keepers of the Maser series of graphic stories, "The 2nd Moon," "The Isle of Dwarves," "Eye of the Sea," and "The Iron Tower." Originally from the pages of Heavy Metal magazine and being reprinted in hardcover by Heavy Metal Press. A lost colony, genetic manipulation of human and animal, neat hardware. Currently at four volumes but obviously intended to continue. "The Isle of Dwarves" also has a nice pictorial guide to the people, animals and hardware of Kolony.
-Phil Foglio's Buck Godot series. Actually a comic book series (of eight issues; supposed to be published in collected form at some point) and a pair of graphic novels (both available again after a long absence). Very funny and worth the effort to find and read. <www.studiofoglio.com>
NOT BOOKS, BUT WORTH A LOOK (OR MORE)
-Farscape, once found on the SciFi Channel on Cable. One human's adventures on the far side of a wormhole. Living starships, lecherous muppet aliens, and more...
-Cowboy Bebop, an Anime series about a bounty hunter pair. Good fun, and more plot ideas than you can shake a stick at (in just the first hour).
-Outlaw Star, another recent Anime release in multiple parts.