Noizio - Feeling that the noise of the big city is too much for you to bear?
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.
Generative.fm - Endlessly unique ambient music
Sounds of Earth - Listen to relaxing ambient sounds of nature
Silenz - Mix ambient noise in with the music you're listening to
Serene - The macOS app to get your focus back