You could start with Jon Udell’s illuminating podcast (mp3, 20MB, 21 min.) where he tells a story about the state of (free) music on the Web.
Or you could start with his blog entry about the podcast which has all the links he mentions in the audio. (So if you’re podcasting, it’s nice to have a transcript with the links.)
And what is a podcast? I know some of you are asking this. Check here for Dave Winer’s official definition or here for the Wikipedia entry. But really, unofficially, a podcast is an mp3 file and you can listen to it with whatever music playback application that you have on your computer (iTunes, QuickTime, or more windows-centric devices).