The Khan Academy is great. But, and I'm not really making any accusations at all, I hope amidst all this praise for what an admirable job he is doing and all the opportunities this affords for underpriviledged people that he stays on top of the quality and accuracy of the material. I just remember there being a few questions about some of his stuff on linear algebra. I also hope he will continue to add more advanced material to the various subjects, but I think that is his plan.