Artificial Intelligence, to be taught in the fall by Sebastian Thrun and Peter Norvig. Although you will not get a Stanford certificate, the course promises a certificate that shows how you would have done on Stanford's grading curve.
I have a technical question about this course and the Khan Academy. Where do they get the tools to create a video in which you see writing on a blackboard, with a synch to audio? I would love to try that out. In the past, I have typed up outlines and attached audio files, but that is not nearly as engaging.
Also, Tim Worstall claims that the University of London already uses this sort of model. Commenters also pointed out that the College Board does some of this with its CLEP testing program. While I applaud these efforts, it seems to me closer to the AP model of "teach to the test" than to what I suggested, which is "test to what you teach," which I explain a bit more in the post where I sketched out A Means A. My claim is that we need flexible and adaptable courses. A system where the test is given and everyone has to teach to it will lack that adaptability. Still, there is much to be said for it. I am a fan of the AP program.