i love jazz when i read...
I'll second that. David Benoit, Earl Klugh, David Sanborn and The Rippingtons are all good.
Classical. Wagner, Beethoven, etc...
Film scores are also good. Especially John Williams (Star Wars, Harry Potter), Randy Edelman (Dragonheart, Gettysburg), James Horner (Titanic, Troy) and Jerry Goldsmith (Star Trek 1 and 5).
It really depends on what you're reading. I like to listen to Jethro Tull while reading "The Lord Of The Rings." Dunno why, it just seems to work well.