iTunes U (as in U for University) is a section of iTunes where you will find a whole host of University courses to download and watch. I mention this to many people and there seems to be very little awareness that all this high quality content is available on iTunes.
There are some great courses available (most for free), in fact I have just finished the Stanford iPhone programming course by Paul Hegarty which I highly recommend.
Thanks for the reply. While I do have an iPhone I try to avoid iTunes (I used it twice to update my phone since I got it two years a go). The programming course does sound interesting though I could use a good course to supplement my self-thought knowledge of the platform.