I just had a chance to check out iTunes U (short for iTunes University) on the iTunes store. I checked out an introductory Computer Science course from Stanford. Actually, it is just the lectures that are placed online as far as I can tell. The lectures are well done and include many major universities. This information should be a great benefit to a large number of people if they are willing to devote time to it.
Lectures in the form of video podcasts seem to be the only content available through iTunes U. However, the lectures often mention the website for the class which can be used for downloading assignments and handouts from the class. This allows anyone to follow along with the class and perform all of the assignments. However, even though you can do the assignments and projects, you won’t be able to submit your assignments for grading. Therefore, there is no real way to measure your progress as you follow a class.
This is a major shortcoming of iTunes U and I think it is their biggest issue at the moment. Without some form of mentoring system to guage students feedback, the value of iTunes U is diminished somewhat. Doing some searching on Google, I did find that some universities have been addressing this issue. Brown University has a page on their Wiki which summarized their discussions on the issue.
Maybe a community of users should get together and do mentoring of students interested in learning online. This way people would be able to take courses online without official credit. It would provide a free means of getting an education for many people. Without any degree from an accredited university, the benefits may seem minor. For technical professions such as engineering, it may be a great way for people to keep their skills up to date.