OCRemix, various classic rock spanning metal/arena to folk. I have some more recent bands but they don't get as much play time. Every once in a while I get on a soundtrack kick and listen to Jeremy Soule (Morrowind, Oblivion, Total Annihilation, Supreme Commander, Guild Wars games soundtracks).
Years ago I was a student of jazz and occasionally throw some of that in there.
I guess basically I'll listen to anything but gangsta rap.