If you're prone to easy distractions in the office or at home and don't find solace in blaring classical or Top 40 tunes from your earbuds, give SimplyNoise a listen. This aptly named site is just that: Simple white (or pink, or brown) noise that comes with options like adjustable volume, an oscillator, and a sleep timer. The basic site is free, but there are "pay what you like" downloads (think: thunderstorms or sea waves) and a 99¢ mobile app available.
So far the brown noise seems to be the favorite at our office, though there's a split decision whether to go oscillating or not. Fortunately, it's all in the ears of the receiver.