With over 3,200 videos
on everything from arithmetic to physics, finance, and history and hundreds of skills to practice
, Khan Academy is on a mission
to help you learn what you want, when you want, at your own pace. The Khan Academy is an organization on a mission. They're a not-for-profit with the goal of changing education for the better by providing a free world-class education to anyone anywhere.
All of the site's resources are available to anyone. It doesn't matter if you are a student, teacher, home-schooler, principal, adult returning to the classroom after 20 years, or a friendly alien just trying to get a leg up in earthly biology. The Khan Academy's materials and resources are available to you completely free of charge.