FORTUNE -- Sal Khan, you can count Bill Gates as your newest fan. Gates is a voracious consumer of online education. This past spring a colleague at his small think tank, bgC3, e-mailed him about the nonprofit khanacademy.org, a vast digital trove of free mini-lectures all narrated by Khan, an ebullient, articulate Harvard MBA and former hedge fund manager. Gates replied within minutes. "This guy is amazing," he wrote. "It is awesome how much he has done with very little in the way of resources." Gates and his 11-year-old son, Rory, began soaking up videos, from algebra to biology. Then, several weeks ago, at the Aspen Ideas Festival in front of 2,000 people, Gates gave the 33-year-old Khan a shout-out that any entrepreneur would kill for. Ruminating on what he called the "mind-blowing misallocation" of resources away from education, Gates touted the "unbelievable" 10- to 15-minute Khan Academy tutorials "I've been using with my kids." With admiration and surprise, the world's second-richest person noted that Khan "was a hedge fund guy making lots of money." Now, Gates said, "I'd say we've moved about 160 IQ points from the hedge fund category to the teaching-many-people-in-a-leveraged-way category. It was a good day his wife let him quit his job." Khan wasn't even there -- he learned of Gates' praise through a YouTube video. "It was really cool," Khan says.
