The New York Times has a nice piece today on university podcasts and how they're turning some professors into international stars. The article gives special attention to Walter Lewin, an MIT physics professor, and highlights courses that you'll find in our listing of free university courses. Just as an aside, the article mentions at least one course that yours truly helped put together.
You can access complete university courses via podcast here. If you want a more comprehensive list of university podcasts (which will give you access to many lectures, but not necessarily complete courses), click here.