My experience with online classes was not so great- I tried two; a writing class and a human developement class (think it was interpersonal communications) Maybe it was just these particular instructors, but I got the impression that in order to compensate for no class-room time they reallyp piled on the busy-work. It was annoying, plus I didn't realize going into it that INTER-personal communications meant communication with yourself so there was a lot of introspective, personal stuff you were meant to write about and then post online- to a bunch of people you don't know (hey- kinda like here! But not as cool.
) Also, one class used a format that was relatively straight-forward and simple to learn anduse and the other was just byzantinely complicated and took me more than a week just to find all the parts I needed just to complete assignments. The teacher freely admitted that she was computer illiterate so I think did a very poor job of organizing the information in an online format.
I'm not sure about legitimate places to take classes from- I took ours from the local college so they're credit classes; transferable anywhere. Maybe look for something credentialed like regular colleges are? This is a very good question; wish I had an answer.