If you're a Windows user, have you tried Sony's free ACID XPress? It's a lot like Apple's GarageBand where you can record your voice and add musical loops. ACIDplanet.com offers an "8pack" of free loops each Friday for ACID XPress. So far, here are the ones I've downloaded over the last dozen weeks: Bon Voyage, Boo Unit, Clean Up, Lambient, Music Theory, Phone Home, Picked Apart, Queep Queep, Rhythmical, Shadow Puppets, Shameless Plug, Skins, and Your Place. The 8packs have fun names--and it's really fun to use the new loops in your podcast!
If you're a Mac user, you too should be downloading the free weekly 8-packs from ACIDplanet.com. Each pack has eight WAV files that can also be used as GarageBand loops. Simply drag a WAV file into your song. Or, drag the folder into your loop browser to add them to your library of loops. In addition, Bitshift Audio is offering 40 MB of free loops for GarageBand. Since these are AIFF files, they can be used in other audio programs, like ACID XPress. If you or your students are tired of the same old loops, I highly recommend these freebies!