If you're a podcaster in Canada you might be interested in Tod Maffin's "A Dummies Guide to Podcasting Music in Canada":

Why can’t I play commercial music in my podcast in Canada?

Good question. It’s the question most most podcasters have been asking me at these meetups I’ve been doing across the country. Let me try to provide some answers. (First the disclaimer: I am not a lawyer. If you want real legal advice you should actually talk to someone who studies this stuff for a living. And then buy them a drink because God knows, they probably need it.)

Tod does an excellent job of debunking some common myths, and telling you exactly what you'd need to do to play music on your podcast.

I haven't paid too much attention to playing commercial music on podcasts, for two reasons. One, we have things like the Podsafe Music Network that contain a very large collection of audio you can use. Second, too much commercial music could turn podcasting back into radio! I figure if you want commercial music, there's satellite radio or iTunes or something. That's just my personal opinion though, and I know there are lots of people who want to play music.

Having said all that, things are still in the very early stages. A year from now there might be really simple licenses for podcasters to purchase, who knows!