AudioFarm

BeatPick

ccMixter

Classic Cat

Free Music Archive

Freeplay

FreeSound

Free Sound Project

Free-Loops.com

Find Sounds Search for sounds and sound effects

Internet Archives Netlabel

Incompetech Royalty Free Music

Internet Archive’s Netlabels Collection

IMAtunes

Jamendo

Musopen

Open Source Audio from the Internet Archive

Partners in Rhyme

Public Domain 4U (lots of blues)

Purple Planet Music (Royalty free music)

Soundclick

Vimeo Music Store (some pay)

YouTube Audio Library