The NYT has a small article in their Sunday Education Supplement about podcasts of lectures at Purdue and other schools. Here is the link to the Purdue Podcasts. I think it will be fun to listen to some of the agricultural ones.
IT Conversations - "New idea through your headphones."
The University Channel- A collection of public affairs lectures, panels and events from academic institutions all over the world
-- for you to view, listen to, stream or download.
The Little Gray Book Lecture series podcasts.