On the Productive Strategies blog, there is a list of lectures from several American universities that are now available through iTunes in podcast format .
Reading through the comments, I also found several other links:
-- videos of MIT lectures along with other free speeches, audiobooks, etc.
-- University of Mary Washington series of "profcasts," beginning with poet Claudia Emerson reading from her new, Pulitzer-prize-nominated collection, "Late Wife."
-- UC Berkeley courses and events
-- downloads from Stanford
-- lectures from Princeton's University Channel
Ever since Jonathan turned me onto IT Conversations last year, I have become addicted to the lectures and talks that I download to my iPod. One of the most interesting and funny lectures was from Frans de Waal about how we as humans compare to primate politics. You can't help but laugh!