Soundsnap is a new place to find sound effects and musical loops. It's like YouTube for sounds because users can download sounds and upload their own--all for free. Everything uploaded to Soundsnap is copyright-friendly for podcasters to use. Here's how Soundsnap describes itself:
Soundsnap is the best platform to find and share free sound effects and loops- legally. It is a collection of original sounds made or recorded by its users, and not songs or sound FX found on commercial libraries or sample CD's.Soundsnap is fully searchable and sounds are also categorized and tagged for browsing.
It was originally started by a small group of sound people from all over the world. Our common belief is that sounds and samples should be free for everyone to use in their projects, commercial or not.
Our users are a diverse mix of sound designers, sound artists, web game developers, filmmakers and music producers. Hobbyists and home video makers are welcome too.
You can download an MP3 or WAV version for most files from Soundsnap. I recommend downloading WAV files to import into your podcasting projects. WAV files are usually higher quality. You'll be compressing the audio later, but it's nice to start with the best sounding audio available.
Soundsnap started with 30,000 audio files and is growing. Check it out!
Update: Soundsnap is very much like YouTube, where not all uploads are appropriate for school. It's probably not a good idea to let students loose on Soundsnap (and it's likely to be blocked at school). I suggest that educators download a whole bunch of useful audio files from Soundsnap to their hard drives and organize them into folders. Burn those folders on a CD or place them on a flash drive that is always available for when sounds are needed.