Moszen - Moszen is a free web service that provides ambient sounds from natural environments to help you relax and avoid stress in your daily life.
Noises Online - Premium masking sounds
Noizio - Feeling that the noise of the big city is too much for you to bear?
SoliCall Pro - Removes noise & echo from any VoIP call. Can also be used for call recording.
Calmsound - Calmsound bring the giant collection of the finest natural sounds that are ideal for multiple purposes like keeping the brain calm, sleeping smoothly, getting relaxed and helpful for tinnitus sufferers as well.
A Soft Murmur - Ambient sounds to wash away distraction.