Just saw this posted on an audio drama group board I'm on. Be sure to verify the legal stuff, etc before using it. But it's a place to start!
Then of course there's also freesound.org (though be sure to keep track of whose sounds you download from there. We have to credit them!)
Here's the post I mentioned:
while brousing a gaming forum I use for the blind a free soundpack
has been produced for free projects and such.
The sounds are not for comercial use, right now you have to do some
weird thing with dropbox to get access to the 2gb file and there is
supposed to be a bigger pack comming out to.
Eventually the file will be hosted somewhere.
but this is for all those doing productions.
loads of free sfx some comercial and some home made.