Education

EdX is perhaps the largest and best organized of the attempts at mass, online education. They have a huge variety of courses, many contributed by MIT, Harvard, Stanford, and other name brands in top drawer education. I've taken more than a few of these courses myself (audited, usually, but the lectures just the same).

Coursera also offers many excellent courses. There is a clear profit motive implicit in the organization of their offerings, but they are also willing to give away their material, so I don't begrudge them an attempt to pay the bills at the same time.

Lynda.com is in a different category than the first two, since their website is clearly intended only for its profit making potential. If you are willing to give them some money, however, you will have access to large catalog of courses. Their offerings are mostly computer/technology- focused, but if that is your interest then paying their monthly fee might make sense.

This website was around long before EdX and Coursera, and the motivation seems to be nothing other then providing sets of lectures over the Internet. Note that this site offers merely lectures, without the test questions offered by EdX and Coursera, and the quality is sometimes uneven. That said they also have some real gems here: this site is still the only place I know of to watch a series of lectures in gross anatomy where a pathologist offers commentary while cutting up a cadaver week after week.