Napsounds is a repository of relaxing audio files designed for power napping. Every day a unique 20-minute track is generated in the electronic, classic, and nature sounds category. You can listen directly from the web site, download the track as an MP3, subscribe via RSS, or set iTunes to grab the track as a podcast. The tracks use a combination of neural linguistic programming, binaural beats, and white noise generation layered into the ambient sounds.
Fair warning: the tracks include a very deep Donald LaFontaine'esque male voice that speaks at the beginning and end of the tracks urging you to relax and then gently awake. While I found the voice to be initially disconcerting— the site made absolutely no mention of the fact that a minute or so into my listening experience a dude would start talking to me— it was helpful to have a human voice appear at the end of the track to stimulate wakefulness. Without it I could have easily slept right through the fading cricket chirps. If you're new to the idea of power napping, make sure to check out the power napping cheat sheet and how to reboot your brain with a caffeine nap.