Salman Khan started out making a few algebra videos for his cousins. He has an amazing gift for breaking down complex problems into easy-to-understand modules. Once he began putting his videos on YouTube they became extremely popular. On Khan Academy's website, there are now more than 2,100 videos and 100 self-paced exercises and assessments covering everything from arithmetic to physics, finance to history. Salman Khan’s TED Talk video is well worth watching.