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.
Medito - 100% Free Meditation App that will improve your Mental wellbeing with the help of Guided Meditations, Breathing Exercises, Mindfulness Practices, Relaxing Sounds, and more.
Noizio - Feeling that the noise of the big city is too much for you to bear?
Headspace - Meditation made simple. Brilliant things happen in calm minds.
zenmix.io - Ambient background sound generator
Breathe Meditations for Mac - Immerse yourself in nature. Increase pleasant feelings.