I got to help teach one! This answer doesn't answer the question that was prompted, but I volunteered for Stanford's Code in Place (introductory CS) and it was

I got to help teach one! This answer doesn't answer the question that was prompted, but I volunteered for Stanford's Code in Place (introductory CS) and it was kind of amazing getting to be on the other side of the MOOC experience as a TA. I lead 5 assigned class sessions with a small group of people (never more than 10) and held 5 other office hour style sessions as well. It was a really rewarding experience and I think a lot of people who can volunteer for it should consider doing so if Code in Place continues.