I listen to a wide combination, really... Most of it is in the rock genres, though. Metal, operatic/gothic rock, punk rock, screamo or emo rock, I listen to some rap but mostly the emotional stuff, some might even call it the emo rap... Uhm, I listen to some old 30s, 40s, 50s stuff like Doris Day, Louis Armstrong, Elvis, etc. But I also go so far as to listen to some pop stuff such as Pink. But then I also go to the indie spectrum and listen to some relatively unknown stuff such as Puscifer or Mae. Oh, but sometimes I get into a weird mood and start listening to comedic stuff like Weird Al, Voltaire or even Da Vinci's Notebook. Oh, and then there's my all inclusive mishmash of electronic/trance/dubstep/etc mood that includes whatever I happen to find that is appealing. Lindsey Sterling in particular catches my fancy for this.
All in all, its just random things that capture my mood at the particular time. My old music collection consisted of 7000 songs and today, if I was still keeping up with it instead of just streaming everything, would be liable to be over 8-9k. Just to give you a rough estimate of just how vast my listening habits could range. >_> <_<