Lifehacker.com had an article on "free courses" available online. Not all are "courses" in the traditional sense - you get materials but there are no instructors or mentors. They are a good source of self-paced instruction and a good way to look at what other instructors and schools are offering.
When classes at MIT were first offered as part of their Open CourseWare (OCW) project, it encouraged other schools to do the same - but there were others on this list that were doing it before MIT too.
The Open University's OpenLearn website has free and open educational resources for learners and educators around the world.
Now that Apple has a number of iTunes U schools, you can go to sites like Berkeley's iTunes U and download course materials (iPod not required).