The University of California – Berkeley has put a bunch of audio lectures on the internet as podcasts. I listened to a few and they are compressed, that is to say the audio quality has been reduced and the top and bottom frequencies taken out to decrease the size of the audio file. It makes it somewhat hard to listen to, but if you turn up the volume on your computer or MP3 player, it should be just fine.
They have a few good lectures on Computer Science topics. I listened to part of the Data Structures lecture. The lectures range from Biology, Psychology, PolySci, History Physics to Art.
Get the iTunes software at Apple.com or if your are in an experimental mood, try working with SongBird.