istockphoto is now allowing contributors to sell audio clips. I'm sure they will do great with this, as they already sell just about every other kind of media.
Royalty Free Stock Photography Community | iStockphoto.com
I noticed a few members from here are already selling audio clips of their own. Are you recording them with anything special? Do you need a special audio recorder, or can you just use a cheap digital camera in video mode, and then just remove the audio from the video file?