My mathematically inclined readers are cordially invited to enroll in "6.SFMx: Street-Fighting Math," which starts today on EdX. Like most (all?) MOOC courses, it is free and open to world, as are all the course materials.
So far, I have learned that teaching an entirely online course requires far more effort than teaching in person. Maybe by a factor of 10. Partly, it is the difference between talking to a friend on the phone---you just pick up the phone and start talking---compared to writing a long letter that needs to be thought out. To this difference you add that 10,000 others will also read and depend on the letter. You get nervous about making all the pieces right. They never will be, so you never rest easy.