Music gives the less writerly-insane parts of our brains something to do while we're putting words on a screen, and soundtracks are an excellent choice. Personally, I used to write to movie soundtracks (the TRON Legacy soundtrack is proof the universe wants me to be happy), but those can be tricky. John Williams' Star Wars soundtracks are amazing achievements but you're working away and here's the Imperial March and now you have to go march around your house like you're Darth Vader.
So for the past few years, I've switched to game soundtracks. Not the Tetris music (can you imagine? I would lose my mind), but the gorgeous and symphonic soundtracks with atmospheres. See, game music has recognizable themes, but also ambient background music, for those less exciting bits when you're running across a vast landscape or staring blankly at a jumping puzzle. This means you get wonderful ambient mood-music drifting through the background.
Want to try some videogame soundtracks out? Here's some suggestions.
Elder Scrolls V: Skyrim: This is my hands-down favorite, and not just because I lost so much time to that amazing game (just talking about it makes me want to go play it some more). The themes in the soundtrack are amazing. The Dragonborn, Dovahkiin theme at the beginning makes you want to go wield and a sword and pillage, but quite a lot of the soundtrack offers you the roaming music of a gorgeous, cold, windswept Nordic world. And it doesn't hurt either that the soundtrack is four hours long. That's a lot of writing time. And if you burn through that four hours and want more then you're in luck, because the same composer did the soundtrack for Elder Scrolls IV: Oblivion and it's nearly as good. (Also, the Skyrim soundtrack is fourteen bucks. For four hours. Talk about value for money.)
Assassin's Creed IV: Black Flag: All of the Assassin's Creed games have had really good music, in my opinion, but I'm fondest of Black Flag's soundtrack. Perhaps because it was one of my favorite games, a wide-open Caribbean world, a pirate ship at your command, plenty of buckles to swash, and so forth. The main theme of the Black Flag soundtrack reminds me (of all things) of the music from the TV show Firefly. The ambient music is great, but there's a strong mood running through it, and through the stronger themes. A soundtrack very reminiscent of the excellent Pirates of the Caribbean soundtracks, this is good music for writing your tense scenes, your action moments. Or, much like Skyrim, you can put it on headphones and make your grocery shopping trips epic and portentous. Up to you.
Mass Effect Trilogy: People rant and rave in giddy enthusiasm about the Mass Effect series of games the same way they do about Star Trek, or crossfit, or the way polite young men come to your door to have a word with you about your eternal soul. Very excited, is what I'm saying. To my shame, I have to say I own but haven't played the trilogy yet, but the soundtracks are brilliant. They of course have a science fictional quality to them, and they remind me of a gentler version of many of the Star Trek soundtracks I have been so fond of for decades now. A trilogy of soundtracks gives you an awful lot of music to work with. I put them on shuffle and wander through. (as a bonus, why not mix in the first Halo game soundtrack? It fits well with Mass Effect.)
Diablo III: My most recent one, since I've been playing it obsessively for a few weeks now. The soundtrack works surprisingly well for writing, despite being deep and doom-laden (a game called Diablo has a dark and doom-laden soundtrack? What?) it's very beautiful and enjoyable music. I haven't become taken with it quite to the extent I am with Black Flag or Skyrim, but still very gorgeous and useful. It's been my writing music for the past week, so it's clearly working pretty well. The add-on game to Diablo III does, itself, come with an hour-long soundtrack which is also very good, so you've got plenty of music here.
There's so many, many more I could go on about. The Uncharted trilogy, the Legend of Zelda games, Super Mario Galaxy of all things, and so on...but the ones up there are enough to be getting on with, I think. Try 'em and buy 'em, put on a good pair of headphones, and I don't think you'll be disappointed.