Moodwill - Create and listen for free to your perfect nature sounds environment with music to help you concentrate, relax, sleep and overall feel better.
Brain.fm - Music designed for the brain to enhance focus, relaxation, meditation, naps and sleep within 10 - 15 minutes of use.
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.
Tinnire - Generative music for productive work from home
Silenz - Mix ambient noise in with the music you're listening to
MyNoise - Custom shaped online noise machines. Many Many generic sounds