Noisli - Noisli is a fantastic background noise and color generator for working and relaxing. Online soothing ambient sounds like White noise, Rain and Coffee Shop.
Brain.fm - Music designed for the brain to enhance focus, relaxation, meditation, naps and sleep within 10 - 15 minutes of use.
Noizio - Feeling that the noise of the big city is too much for you to bear?
A Soft Murmur - Ambient sounds to wash away distraction.
MyNoise - Custom shaped online noise machines. Many Many generic sounds
Rainy Mood - Rainy Mood is the world's most popular rain simulator. Sleep, study, and relax with the sound of rain.