I've noticed a flourish of academic podcasts coming directly from universities. Check out this Newsday article on the phenomenum. Here are some of the sites and meta-indices I've come across:
Thomson Academic Feeds Directory
Strategy-Blogs's List of Academic Podcasts
Princeton University Channel
Haven's Center at UW-Madison
MIT's Open Courseware
Over the next couple of weeks, I am going to give a closer listen to some of these lectures and tell you what I think. If anyone knows any other sites or particularly enjoyed one on these lists, please let me know at: firstname.lastname@example.org
Update: Here are a couple more universities with Open Courseware.
Update: Vanderbilt Podcasts, Berkeley Podcasts, and Carleton University Trial Chemistry Vodcast.
AskMeFi post on educational podcasts.