Khan Academy is the brainchild of Salman [Sal] Khan. The site is a not-for-profit 501(c)(3) with the mission of providing a world-class education to anyone, anywhere. To-date, 35,263,068 lessons have been delivered on the site with videos, exercises and other tools. It contains a library with user-paced exercises–developed as an open source project–allowing the Khan Academy to become the free classroom for the World.
This is an excellent site for anyone wanting to learn on their own on the web. [link]