High school Anatomy and Physiology teacher Jodie Deinhammer has used Itunes U for her high school classes, and says she "cannot imagine teaching without it." You'll find links to her Itunes U course, as well as a link to a course her students created.
Bear with the initial sound issues (only the first thirty seconds or so), because this is a really helpful recording of a hangout in which two teachers show, step-by-step, how they set up iTunes U courses.
In this polished video tutorial, school technology specialist David Hotler explains why you should use iTunes U in the classroom, and how to use it. He makes the point early in the video that iTunes U is more of a curation tool than a full-featured LMS. In other words, it isn't like Blackboard or Moodle.
This course for high school students provides lesson plans and presentations to teach students to design and code iOS apps using the Swift programming language. This course would only work for fairly advanced high school programming students, but I included it as an example of a high school course.
Co-founder of Coursera Daphne Koller discusses the future of learning in this Wall Street Journal article. She discusses the fact that "real" physical classrooms will not become obsolete, the fact that online learning is less expensive, and the problem of potential cheating in online courses.