I think everyone has heard of the Khan Academy by now. But, just in case you have not, we are into education today and this is a great site — all free.
Excerpt: A free world-class education for anyone anywhere.
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 for 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.
Check out the possibilities via About | Khan Academy.