A bit weird perhaps, but depends on what I have to code.
Usually, mix of minimal techno, drum and bass, and trance (old-school trance). That stuff really gets me in the zone and lets me forget the time for at least a couple of hours. Especially minimal techno mixes.. they are like.. they continue and go on and on and I don't really sense switches between tracks, so it feels like my coding is also continuous.
When I'm doing research (looking for libraries, reading API, etc.), I usually like to listen to something more melodic, like jazz or classical. Dunno why really.
And occasionally some retro music for dem feelz and nostalgia... Charlots of Fire anyone?