When I need to focus on a task at work, I like to listen to ambient music. Sometimes I just need some soothing white noise while I go through some metrics.
SimplyNoise is a white noise generator that you can use on the web or on the iPhone.
When I first got on the site, it was set to "white noise" and that just sounded like pure static to me. I currently have it set to "oscillating" (the blue button on the right) and it's producing a pleasant, waves crashing on the beach kind of sound.