So... sticking with the topic of sleep (can you tell it's on my mind lately), this nice little app is basically a white noise generator. I actually use it mostly for reading or working when I need to tune out other people in the room, the television, and/or other distracting noises--- but you can also use it to create a soothing sound to help lull you to sleep.
Relax and Sleep contains 49 different noises you can mix and match to create the perfect combination for you. Noise categories range from nature (ocean, rainstorm, forest birds) to various humming appliances (running dishwasher, large fan, air conditioner) and everything in between. You can also save your favorite combinations, generate a random combination, and set a timer for how long you want the noise to continue. Pretty neat!