When I'm coding I mainly listen to classical music. The problem is that I need to listen to things I know very well or I'll get distracted, so I end up listening to the same compositions over and over again, to the annoyment of my wife ;-)
These days the compositions I list the most while coding are:
- Beethoven String Quartets, for instance  (I really like the fugato at 5:00 ;-)
- Mahler Symphonies, for example 
- Ravel music
- Some Monteverdi madrigals 
I like to use headphones, either a Sennheiser PX 200  or a Sennheiser HD-280 PRO .
I've found that I am pretty productive in a cafe these days, so I started listening to tracks of cafe background noise when I work from home recently, such as "People Talking in Coffee Shop" by Finnolia Productions .
Might write more about this if it works well enough.
 iTunes affiliate link: http://click.linksynergy.com/fs-bin/click?id=dE0y3GuqVK4&...
I listen to it everyday and never get bored :)
turntable.fm's "Ambient Chillout & Trip Hop" room is usually quite good.
di.fm - Chillout, Minimal or Ambient
bassdrive.com (liquid dnb)