The Canadian indie label Constellation has a number of artists that make good coding music, including Godspeed You! Black Emperor, Thee Silver Mt. Zion Memorial Orchestra, and Do Make Say Think.
Other relevant artists include: Mogwai, Boards of Canada, Dirty Three, Explosions In The Sky, LCD Soundsystem, Monolake/Robert Henke, The Necks, Ratatat, The Flashbulb, The Samuel Jackson Five.
There's a few particularly good movie soundtracks I like, as well: Koyaanisqatsi, Le Fabuleux Destin d'Amélie Poulain, and Blade Runner.
Another good source of quiet, interesting, music is videogame soundtracks. I'm particularly fond of the soundtrack to Ōkami, and the OCRemix tributes to Donkey Kong Country, Super Metroid, and Doom: http://ocremix.org/albums/?&offset=0&sort=nameasc
Boards of Canada, Explosions in the Sky, Ratatat, F*ck Buttons, Tortoise, and El Ten Eleven have been in constant rotation for me lately. I often use them as seeds for Pandora as well. Works like a charm.
Edit: fixed URL.
For coding I usually pick techno, electronica, soft rock, classical, or more piano/instrumental types. It mostly depends on mood. I tend to avoid things with lyrics for coding.
More specifically, I've been addicted to Explosions in the Sky and Trifonic for months now.
I also love Buckethead. Energizing!
Examples, Tool, Pink Floyd, Rage Against the Machine, In Flames, etc.
edit: also, almost any station from SomaFM http://somafm.com/
These two plus the aforementioned NIN Ghosts I-IV and the Social Network score are in heavy rotation.
something like that...
It's all instrumental and is somewhere in between Explosions in The Sky and Boards of Canada.
NIN, RHCP (the soft stuff), and trance.