Cory Doctorow mentioned using Freesound Project to find sound for his Little Brother podcast. Wow! Think Flickr for sound. AIFF and WAV files listed and geo-tagged! For a sound buff like me this is heaven with a URL! Check out this map, it shows exactly where the sound was recorded and lets you download the file. MTG has recently won a $50,000 Google Research Award so Freesound Project will likely, at some point, be acquired by you know who. ;)
Click to enlarge.