I wrote about the Khan Academy as a magnificent obsession. Considering how big it is I could have written about it as if it is one of the net's obvious sources.
Sal Khan gave a presentation at Gel 2010. He gives more insight into how the Khan Academy was started. And as he talks with the audience he points out some of the things he ended up doing right even if those things weren't intentional or planned. It's a good place to start knowing more about the person who's going to end up having taught a lot of the world a lot of subjects.