Minimize Desktop Distractions, article about several different Mac applications which help to minimize distractions when working on the computer. (I blogged about this issue a few months ago, and alert readers helped me find some of these.)
I bought one of the slightly pricey "white noise" MP3s. They are misnamed, because real white noise is featureless noise of all wavelengths mixed together, just like white light. These, instead, are recordings of noise like for example a rain storm like the one I bought, and which I quite like. It seems relaxing somehow.
... Actually I just realized that these MP3s can help me with a problem I have recently: my upstairs neighbor, despite his willingness to solve the problem, sometimes is not home when his clock-radio starts in the morning, so I have to listen to it for two hours, and it's just loud enough to irritate me and stop me going to sleep again. I don't like wearing earplugs. I think an iPod with these files plugged into the high quality Soundsticks II speakers in my bedroom will do the trick.