I've gone on record as being against individual offices and for working at a standing desk in a common space with colleagues. To this I generally get two different kinds of objections: first, "but I have all sorts of confidential calls to make" to which I reply, "go find a conference room or phone booth." The second one is, "but I can't concentrate with all that noise" to which I used to say, "headphones, dude." But I've come around to the belief that listening to music isn't always the best way to block out the outside world and focus, but neither is locking yourself away in total silence. It turns out there's some science to back me up.
I've tried a few different methods, and these three sites are good examples of some different approaches to soundtracks for focus. They also help make sure you're not that guy in the office singing along tunelessly and obliviously to whatever's in his headphones. Or so I hear.
simplynoise - just like the name says, just noise. Well, not quite just noise, and not quite any noise. Simply Noise offers white, pink and brown noise (NOT the same as the brown note) at steady or oscillating volume from a website or mobile app. Some people love white noise and some absolutely hate it, but I think all can agree that it does a decent job of muffling other sounds and rendering nearby conversations less intelligible and therefore less intrusive. I think these noises can also help people sleep in noisy environments, sort of the opposite of the goal I had in mind.
focus@will - these folks have added a layer of actual neuroscience onto the basic background music business. Focus at will offers music programs engineered to help you achieve flow state and stay there. I can't evaluate the science but I must say that I've found it effective. The music is not what most would choose to listen to, but the idea is that paying too much attention to the music is itself bad for productivity, so it's supposed to inhabit some kind of in between space. The science section of the site says, "part of the trick is occupying your brain just enough to let you work."
Coffeetivity - at first it's hard to say if this is a put-on or a serious contender. Perhaps it started as one and evolved to the other. Using the same underlying idea as focus@will, that you need something more than silence and less than your music library. The Coffeetivity crew just presents a sound loop of coffee shop hubbub to accomplish this task and keep you on task. If you don't care about the science but have gotten into the habit of working in a coffee shop, this could give you the audio fix you need when you can't get to a coffee shop but have to work.
There are probably a ton of productivity soundtracks and methods beyond simple noise, scientific music, and cafe commotion, but I keep coming back to these three for helping me get to flow when the job requires it. Your mileage may vary, of course.