www.soundsnap.com
The idea is very nice. The FX can be used freely in either non-commercial or commercial productions... I've only listened to a couple of sounds, most were poor quality, but there were also some good sounds. Another nice thing is you don't have to register or log in to download!
And another one, this one requires registration to download though (not such a big deal offcourse):
http://freesound.iua.upf.edu/