I choose the music style according to what I feel like in a given day, but here are some favorites:

Dark Ambient: Lustmord, Gustaf Hildebrand, Robert Rich

"IDM": Aphex Twin(anything choosen from what I have) and Autechre

Metal: Burzum(filosofem), Xasthur, and mostly atmospheric BM

Industrial: Suicide Commando, VNV Nation, SPK

(Fin)NRG: Alek Szahala and Nomic

Classical: Bach, Handel, Liszt and Chopin

Demoscene music: Bitfellas radio

I will generally create a mix of from the above styles in a playlist and listen to it, when it begins to bother me (after some hours) I'll just change music style.

Also sometimes I just get some game CD and listen to the tracks, usually I choose Total Annihilation.