Couple of my recommendations off the one book shelf I can see from this computer:

Personally I think Lord of Light is Zalazny's best work, but he has a couple other stand alone books that are pretty good. I think that anyone who is going to be an Imm here should read this book. While you are on the Z's, there is a Russian writer (I want to say Zamyatin, but I am probably butchering the spelling) who wrote We, a pretty interesting Russian writer meets Orwell type book, more Sci fi than I think you are looking for.

I also agree with the comments on Brust, although I think he has gotten a bit verbose in his later works. The first few in the Vlad series were quite brilliant. I personally find Eddings and Brooks to be a bit derivative. David Gemmell was quite a good writer, sad to say he passed this summer.

If you haven't read any Terry Pratchett, I recommend him. There are a lot of layers in his works and to me they are a bit like grown up Piers Anthony Xanth books.

Personally I like some of Silverberg's old stuff, the Valentine series was nice and he has a few other good books, both SciFi and fantasy. Orsen Scott Card has some brilliant books, and some crap imho - the Ender books and the Alvin Maker ones are excellent, the others are hit and miss. For a blend of fantasy/SciFi, look for Varley's Titan/Wizard/Demon series, which although somewhat influenced by Clarke's Rama books, are still really interesting psychological studies.

I personally really enjoy pulp from the 50s or so, and while Moorcock was great (and a little later) don't forget about Burroughs, Leiber, Haggard, Lovecraft and Baum (frankly if you have never read the original Wizard of Oz books, you are missing out.)

For female writers, LeGuin is incredible in terms of someone you have to read several times to figure out what she means. Morgan Llewellen is really nice for her historical and Irish bends, and I don't think she has written a bad book. She has some nice fiction for kids also. I like the Riddlemaster of Hed series by Patricia MacKillip. The first few Dragonrider of Pern books are good, but they get old fast to me. Paula Volsky came recommended to me by Yano, and though I only read one of her books, I liked it.