Some of these are super cool, for example www.coursera.com
From their "About Coursera" page: "We are a social entrepreneurship company that partners with the top universities in the world to offer courses online for anyone to take, for free."
And there are funny ones too, like www.Lamebook.com and www.PassiveAggressiveNotes.com ... anyhow, enjoy.
50 Best Websites 2012
TIME's annual salute to sites and services that keep you entertained and informed, save you time and money — and maybe even change your life
http://techland.time.com/2012/09/18/50-best-websites-2012/?iid=tl-article-mostpop1