Shame on you if noone has heard of
www.slashdot.org and the /. affect.
SlashDot is a site where nerds submit stories, and the /. affect is where a site's URL appears on SlashDot and the sheer volume of people now going to the URL from SlashDot crashes the server.
There is one problem with it though as all the user-submitted stories go for moderation and editors decide which stories should get the publicity, and which don't. Which is nice if you agree with the editors but generally it doesn't give much power to the masses, so someone came up with
www.digg.com
Basically people write stories and all the raw submissions are available for the masses to rate themselves. You increase it's dig rating and if the rating gets big enough it can make the main page.
I don't think SlashDot can be replaced, but this is a good compliment.