Learn almost anything for free.

One of the traits of a great teacher is that he can take an idea, distil it's essence, and communicate it to his audience in an easy to understand way. Recently, I've found such a mentor at the Khan Academy. Basically it's this site with a vast collection of Youtube videos (more than 2400 at this junction) on a whole lot of diverse topics, all created by one man - Salman Khan. Most of the videos are just him speaking in the background, along with some doodling on screen, there's no fancy animation or things like that to distract you.

Some may question if you can ever learn something useful from these short clips. But hey, if even Bill Gates is a fan, this guy must be doing something right.