Recently I got an ipod nano and started checking out podcasts. I almost never listen to the radio any more because as Brian Tracy recommends - I've turned my car into a rolling university! Sounds corny but it's really cool and here in the Atlanta area where traffic is hell, it makes the drive so much easier when you feel like you're learning something instead of just wasting time crawling down the highway.
One of my favorite recording podcasts is the Project Studio Network. Sort of like Car Talk for recording geeks. Great reviews, interviews, and links to free stuff, which they somewhat annoyingly always announce with a freeeeee exclamation.
Car talk has a podcast and so does Garrison Keillor with the Prairie Home Companion. All free!
CD Baby has one - covering marketing, recording, performing, touring. CD Baby is a great company by the way for distribution of your CD or arranging downloads on iTunes etc.