Freesound Project is a collaborative database of Creative Commons licensed sounds. The Freesound Project aims to create a huge database of audio snippets, samples, recordings, bleeps.
It allows you to browse the sounds in new ways using keywords, a “sounds-like” type of browsing, up and download sounds to and from the database, under the same creative commons license and interact with fellow sound-artists!
Remember these are not songs, or compositions, but only sounds. Field recordings, kit recordings, generated sounds, … as long as the sounds are not copyrighted.
If you have audio samples and sounds which can be released under the Creative Commons Sampling Plus License, you can add them, after labelling them correctly and help build a huge database.