My favorite of the bunch, an application I myself use on a daily basis. I have plans to expand on this app a lot in the future (more noises, backgrounds, alarm clock, etc...) so do yourself a favor and grab this one while its still $0.99!
"Sit back. Relax. Add some calming ambiance to your surroundings with Rainy Day, a white noise generator for your Android device.
Fall asleep more easily and enhance your music with Rainy Day today! Enjoy the longest and highest quality ambient noise the Android Market has to offer!
-Very high quality rain loop!
-Built in customizable backgrounds!
-Rainy Day continues to play in the background even if you leave the app, allowing you to use your phone while you enjoy the soothing sounds of rain.
-Rainy Day lets you listen to your favorite music simultaneously!"