A friend of mine just told me about this site:
http://www.archive.org/movies/prelinger.phpIt's the Prelinger Archives. Lots of educational, industrial, and amateur films and feature films, and it appears they're starting to get more B-grade movies up there, too. They've got a lot of classics, horror, film noir, hot rod, exploitation, etc. These aren't wav files, but the entire films, audio and video! Download the MPEG and use QuickTime Pro to make audio snippets. Looks like I've got some work to do!