You may think it's odd, but I sometimes listen to video game soundtracks while I work. It's just the kind of thing I need to trick my hindbrain into thinking it's playing a game while my thinking mind, undistracted due to the lack of lyrics, continues focusing on LINQ statements or database triggers.
There are a lot of good game soundtracks. I've stopped listening to the music from Castlevania: Symphony of the Night, although I couldn't tell you exactly why. Today, I'm listening to the soundtrack from The Legend of Zelda: Wind Waker. The Molgera Theme is without a doubt my favorite track. It makes me want to pull out a keyboard and teach myself to play that lead melody. And of course I occasionally listen to the Beyond Good and Evil soundtrack. Although a lot of those songs aren't ideal for casual listening, I really like Akuda House Propoganda.
The soundtrack to Silent Hill 2 is a very good one, although many of the songs are not pleasant to listen to, which is I suppose the point. A lot of them sound like Nine Inch Nails. Silent Heaven has got to be the most beautifully unsettling track on the album. It starts with discordant strings like Freddy Kreuger playing under the hood of a piano and moves tunelessly into an odd pulsing sound which abruptly drops silent a few times before becoming a pulsing bass. At 1:30, the mechanical walker sound starts and it's just plain disturbing. Love it.
The song The Poet and The Muse from Alan Wake is what got me into The Poets of the Fall, but the Alan Wake soundtrack is only like 40% listenable for me.
My go-to soundtrack for coding is the soundtrack from The Misadventures of P.B. Winterbottom. The way the composer has worked time, old-timeyness, and clock ticks and chimes into the music is pretty ingenious. And the lyricless music is great when I just want to put my head down and focus on something. (listen)
Another good ambient music selection is the soundtrack for Minecraft. And Tommy Tallarico's soundtrack for Advent Rising is excellent, despite the steaming pile that was the actual game.
But of all these, the one I listen to most often is probably the soundtrack to Shadow of the Colossus. It's classical music, no lyrics, and it's very well done. That said, my favorite may still be the Bastion Soundtrack. While it's got some songs with lyrics and is thus a bit more distracting than classical music, the harmonies in the lyrical tracks are amazing.