By Arnold Kling
Walter Antoniotti has compiled a big list of free online textbooks in economics, business, statistics, etc.
Also, at the Institute for Humane Studies course, a student from Carnegie-Mellon recommended that university’s open courseware. Unlike MIT’s, there is some genuinely well-thought out interactive material there. I liked Introduction to Statistics quite a bit. The CMU economics intro was oriented around experiments, which might appeal to some people more than others.