WIKIPEDIA
Jimmy Wales
Wales hates the term crowd-sourcing, but his Wikipedia site is the best example of it. Sorry, Jimmy. Wikipedia now has 11 million articles, and there are 262 language editions. Or 265. Depends on which Wikipedia page you believe. Ahem. (Story continued below...)
FACEBOOK
Mark Zuckerberg
Facebook has more than 120 million active members, although it can't figure out how to turn all those eyeballs into dollars. Zuckerberg claims he doesn't care about the money. His investors probably wish he'd stop saying that.
DIGG
Kevin Rose
Simple concept. You submit a link to a story; others vote it up or down. The best stuff rises to the top, and Digg runs ads. In other words, it's a lot like a newspaper, except the editors work for free. And it's not going broke. At least not yet.
LINUX
Linus Torvalds
Thousands of hackers from around the world contribute bits of code for the Linux operating system. Torvalds, who started the project in 1991 while in college in his native Finland, oversees development from his home in Portland, Ore.
YELP
Jeremy Stoppelman
Regular folks rant and rave about restaurants, bars, movies, you name it. Should you really choose a primary-care doctor based on the opinion of random, anonymous 20-something strangers? Of course not. But people do.