sorry about the link, stumbleupon is a bit difficult with sharing links. but this list of sites is SUPER interesting.
coursera - a site of free online courses
freerice.com - answerquestions on different topic - world landmarks, english vocab, languages, maths timetables and donate rice for each right answer.
unplugthetv - instead of watching TV, you should watch.....
TED and lifehacker are also on that list. so's khan academy (actually its the first one on the list)
there's FOURTY sites. I'm definitely sure you'll find something to your liking.