I've taken two classes online, however they were both English courses (one was on Edgar Allan Poe, the other was on Stephen King). The way my school did it was that you were assigned a reading each week and then required to post to a discussion board by a certain day. Personally I enjoyed it, however I think the nature of the classes made them easier to take online. My sister took Calculus online, and like ElleBee said, she had to be online at certain times which made it more difficult. Also something like math probably isn't as conducive to online learning as English may be.