iTunes U lets students (or anyone, really) listen in on lectures, classes and other programs from the world's top educational institutions. In fact, more than 800 universities participate, and this week Apple announced the delivery of 300 million iTunes U downloads.
Students can use iTunes U to find lectures and other materials related to their studies, of course, but really anyone with an interest in continued education can browse the store's contents for audio or video that meets their areas of interest. For example, here's a collection from the Stanford Historical Society, and another from Japan's Keio University. All iTunes U content is free.
Congratulations to Apple and the participating institutions.