I've been fumbling in slow motion through Professor Ghrist's Calculus MOOC on Coursera (
https://www.coursera.org/course/calcsing), and while I find it challenging it's quite enjoyable. His presentation style is quirky and his manner of speech...unique, but he presents concepts in a very compelling and lucid fashion. It's obvious he and his team have put a tremendous amount of effort into the class, and it's especially apparent in the videos.
I enjoyed reading about what he does the rest of the time: unsurprisingly he is doing interesting things in applied math. Thanks for posting this kjak, I wouldn't have discovered it if it hadn't come up on HN!