Digital broadcasts of university level courses have been around for a while, but they never seem to have really caught on with the general public. If you haven’t explored these resources, do it now!
Anyway, one of the first of such courses I dropped in on was an introduction to physics by prof Walter Lewin (I always wanted to be a physicist but never did anything about it), and it was surprisingly engaging. Now, you can catch the audio version of Lewin’s physics class as well as others right in iTunes.
I had no idea that iTunes offered this service, and being as I’m going through an audio-book obsession, this is perfect: