I'd like to see a version of Wikipedia with prerequisites. Each article would list the articles you'd have to know and understand in order to understand the current article. It would also store which articles you'd already knew, and show for which articles you'd be ready, much like the knowledge tree in Civilization (the game). This would work best for the exact sciences, since most articles don't have prerequisites.

For instance, given the article about the Heine-Borel theorem (http://en.wikipedia.org/wiki/Heine-Borel_theorem) I'd love to know which articles I'd have to read before it will start to make sense.

About personalized education: I think it's going to be huge, (good human teachers will always be better, but who can afford private sessions with good teachers?). I'm working on it as well.

But you need a lot of knowledge about the domain you're teaching, apart from all the usual technical bagage. Finding co-founders or employees with both these skills is awfully hard.