Here is a great, short(ish) video from Ted.com describing how Stanford University offered an online course in Artificial Intelligence to over 160,000 students, in 9 countries.  The speaker is Peter Norvig (one of the two instructors) and some of his insight regarding student motivation, the power and necessity o f collaboration and accountability are excellent.

One of their students commented at the end, “This felt like sitting in a bar, with a really smart friend, explaining something you haven’t grasped yet, but you know you are about to.”

Highly recommended: http://www.ted.com/talks/view/lang/en//id/1487