The Khan Academy is a "not-for-profit with the goal of changing education for the better by providing a free world-class education to anyone anywhere. " Designed as a type of educational tool and a living archive, the site contains over 2100 videos that include algebra lessons, calculus sessions, cosmology, and developmental math. The "tool" function comes in when visitors discover that they can create their own playlists of these videos for use after signing up for an account. It is a remarkable collection, and other subjects are covered here as well.