My absolute favourite album to code to would actually be the Tron Legacy soundtrack by Daft Punk, but I've also spent the last few years at uni listening to http://www.prettylightsmusic.com/ while I code: his albums are all available for free/donation, and the genre is kind of down-tempo electronic. There's the occaisonal vocal sample, but I've found it doesn't distract me from work.

Endtroducing by DJ Shadow is also worth a listen, as although there's vocals, they're generally calm. Example: http://www.youtube.com/watch?v=32X-ieCav-M