Sound Download Sites
CC0 licensed (Public Domain)
- Freesound Project
- Machinae Supremacy
- Freesound - Large library of various sound effects.
- Soundbible - big library of sound effects under various licenses (including CC0 and Personal Use Only)
- OpenGameArt - library of free models, textures, music, sound effects etc...
- Wikimedia Commons - large library of various images and sounds under various licenses.