* lolcats
* rage comics
* anonymous
* a lot of the 1% movement
* getting random people in jail because they think animal cruelty is funny
* making Moot TIME's person of the year and getting him a TED talk -> http://www.ted.com/talks/christopher_m00t_poole_the_case_for...
While most of what goes on there hinges somewhere between vile and horrible. 4chan has a lot of good in it, plenty of times there can be surprisingly good and high quality debates.
And come on, it's where all the memes are born. That's profound. What other startup can claim to be such a big influence on western society?
PS: 4chan has also invented a clever sorting algorithm - http://dis.4chan.org/read/prog/1295544154
PPS: sometimes they even manage to count to 10. I think the record was 100.
edit: when I say meme, I mean "A meme ( /ˈmiːm/; meem)[1] is "an idea, behavior or style that spreads from person to person within a culture."[2] A meme acts as a unit for carrying cultural ideas, symbols or practices, which can be transmitted from one mind to another through writing, speech, gestures, rituals or other imitable phenomena." ... I don't mean, "funny picture".
A lot of responders misunderstood this, I think.