I know this is a bit late, but I only just found the thread!
Podcasting is basically a new way of delivery radio content so that you can download using the blogger style RSS function. What makes it different from radio is that you download it to your computer (and then into your iPod if you so wish) so you can take the content away with you and listen at your leisure.
I've just completed a little paper-ette thing (MAed module) on podcasting to teach tunes. Check it out and also the accompanying website.