Geez, I just got started with MadMariner's new "MadCast" podcast series, and they're excellent. You can listen to them right at MadMariner:
http://www.madmariner.com/podcasts
...or via iTunes (hints: search the iTunes Store for "Mad Mariner" not "MadCast", and look for the downloads on your iTunes podcast list under "BTR: Mad Mariner's MadCast").
I just listened to Jeff Siegel on cell phones and Mark Doyle on e-charting. Great stuff!