zenmix.io - Ambient background sound generator
Studiowave - Chillout tunes and inspiration
SoundDrown - Ambient sounds to help you focus, relax, and escape
Defonic - Create a unique sound environment at home or in the office
Moodwill - Create and listen for free to your perfect nature sounds environment with music to help you concentrate, relax, sleep and overall feel better.
Ruya - A calming space