MIT might be popular with it's OCW online course, but right now, there are a lot of online site that offer the same service (free education for public). This could help people who are unable to attend normal class session, but they have the spirit to learn more from the online tutorial or students who are looking for additional resources to learn something that they don't get in their courses.
One of the site that i like is Khan Academy, a non-profit organization that has a goal of changing education for the better by providing a free world-class education to anyone anywhere.
So far, they have more than 3000 videos and 311 practices and these number are increasing as time ticks. They divided into three big categories: Math, Science, and Humanities & Other. Below this main categories, lies more sub categories, such as Algebra, Computer Science, Physics, Biology, Chemistry, Finance, etc.