TED (free)

TED is filled with more than 900 on-demand videos of experts around the world giving talks about various topics. Subjects range from "Five ways to listen better," to "How algorithms shape our world," and "Building a dinosaur from a chicken."

Intimidated by these topics? Don't be. The most addicting part of TED is that these experts have a way of presenting otherwise complicated topics in an understandable way.

Available for iPad, iPhone, and iPod Touch.