game-editor.com

Interesting place to find all kind of sounds for your game.
http://www.freesound.org/browse/
http://www.shockwave-sound.com/

Atmosphere Deluxe is an ambient soundscape generator, great for background sounds. DIfferent versions available. The demo is awesome. It make you feel you are somewhere else.

http://www.vectormediasoftware.com/atmdeluxehome.htm

and
http://www.vectormediasoftware.com/soundmaskerhome.htm

Awsome. +1