James Wyatt - DotF, Deities and Demigods, Oriental Adventures, I own em all and get a lot of use out of OA. DotF was a great resource when books of any kind were scarce, and Deities and Demigods just seems like a good back to have laying around in case characters get too cocky...
Bruce Cordrell - Psi Handbook, Speaker in Dreams, Tome and Blood, I own all of these and use the 2 supplements often. The adventure I have run through as a player and ran as a dm twice.
Sean K Reynolds - Forgotten Realms Campaign Setting, Magic of Faerun, and Lords of Darkness. I own all of these (a pattern forming here?) and get extensive use out of FRCS and MoF. Lords of Darkness is there for me when I start DMing again, tons of ideas.
Monte Cook - Call of Cthulu and the DMG. I use the DMG more than any other book Ive listed, and while he didnt do it on his own, I believe without his influence we would all be playing a very different game (note: this can also be said of the other core designers Skip Williams and Jonathan Tweet). Call of Cthulu is also the only non-core non-forgotten realms supplement Ive bought besides Oriental Adventures. I think its awesome and it got me into an entire sub-genre of books (not entirely due to his presentation of the game, but I think its an interesting flex of the d20 muscle).
There are certainly others, but generally those are the names I look for when buying new books/adventures. I realize I am heavily biased towards WotC employees or former WotC employees, but thats just the way I am. Non-WotC stuff never seems to blend in as well, which is probably a failing on my fault.
Technik
PS OT: I dont know how to post a poll, but would someone please start one about peoples reaction to a hardcover combined splatbook book. It would include Sword and Fist, Defenders of the Faith, Tome and Blood, Song and Silence, and Masters of the Wild. It would include the most updated prcs, feats, spells, and items consistent with Revised 3E, and would include 10-20% new information, things in erratta that couldnt fit in the books originally or things that mesh well with the overall concept. Poll options:
Buy it Immediately
Wait and See
Refuse on Principle
If someone could do that, that would be awesome, thanks.