The Khan Academy is truly an amazing startup. However, I think it is important to note that it is actually a 501(c)3 nonprofit. I'm sure Sal Khan has been approached by many VC's, but thankfully he has not gone for turning the concept into a for profit company. The technology, especially the "coach" dashboard, is very impressive and is already being used by teachers in classrooms around the classroom and country.

KhanAcademy recently won the Google Project 10^100 which got them $10 million. I expect to see great things from this site in the coming months.