I saw an article about Sal Khan a couple of weeks ago in Times magazine. I think it was the version where they portrayed the most influential people of the year 2011. On of the persons of 2011 was Sal Khan, the founder of an online academy. I was interested and had a look at the web site and was immediately impressed.
Now I am watching more and more videos. I am especially interested into the topic economy where Sal explains a lot about the current problems of US economy. But I also already watched videos about biology, maths and history.
The videos are about 10 minutes and Sal is able to explain things so easy that everybody should be able to follow him. I even able to follow him though its all English.
The most impressive videos so far were about evolution, bankruptcy, US elections and so on. Very impressive!