What does the Khan Academy offer? The tagline on the academy’s website says it all: “A free world-class education for anyone anywhere.” Now, with the Khan Academy app for the iPad/iPhone, anyone in search of that free education can find it on his/her portable device. The Khan Academy app gives users access to the academy’s entire library of educational videos, which totals more than 3,500. The educational videos are organized into four broad categories: math, science and economics, humanities, and test prep; in turn, each of these umbrella subjects contains countless subcategories. Videos range in length from just a minute to 20 minutes or more. Each is subtitled so that viewers can skip ahead or back. In addition, app users can share the videos via Facebook or Twitter, and can also download the videos to their devices (by default, the videos are viewed over a Wi-Fi or 3G connection).