The Khan Academy is an organization on a mission. We'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.
With over 3,200 videos on everything from arithmetic to physics, finance and history and hundreds of skills to practice, we're on a mission to help you learn what you want, when you want, at your own pace.
Website: Khan Acadamy
Wiki Page: Khan Academy