Noizio - Feeling that the noise of the big city is too much for you to bear?
RecordGram - A studio and production marketplace in the palm of your hand
Defonic - Create a unique sound environment at home or in the office
SoundBetter - Marketplace for musicians and music production professionals
A Soft Murmur - Ambient sounds to wash away distraction.
Soundsnap - Shutterstock for sound effects