Sean Parker

Facebook

Estimated net worth: $920 million

Cofounder of Napster and Plaxo, Parker was the Silicon Valley veteran who joined Facebook in 2004 as its founding president and helped it navigate initial funding. He left in 2005 for venture capital but still has a 4% stake. Justin Timberlake plays Parker in the upcoming film The Social Network.

Mark Pincus

Zynga
Estimated net worth: $850 million
Love-him-or-hate-him leader of Internet's most popular gaming site, Zynga, named for his late bulldog. Pincus' fourth startup, it grosses some $500 million from virtual goods and promotions with 7-Eleven, Target, MTV. "FarmVille," "FrontierVille" and "Zynga Poker" are its most popular games.

Jerry Bruckheimer

Movies, TV
Estimated net worth: $850 million
The Hollywood producer's blockbuster franchises, like Pirates of the Caribbean and National Treasure, have generated $9 billion at the global box office, with more to come. TV hits include the CSI franchise, Without a Trace and Amazing Race.

Jerry Seinfeld

Television
Estimated net worth: $800 million
His TV show about nothing has earned $2.7 billion in 12 years and could take in $200 million more a year, thanks to syndication payments. Seinfeld has spent some of his portion buying up New York real estate and has a four-car garage (in Manhattan!) for his fleet of vintage motors. The cash-rich star may need another hit: The Marriage Ref wasn't it.

Eric Lefkofsky

Groupon
Estimated net worth: $750 million
Chicago investor is cofounder and 30% owner of the fastest-growing company ever, Web phenom Groupon, which updates its online audience about deep discounts on products and services. His venture fund, Lightbank, has stakes in 11 companies, including two now public ones: Innerworkings and Echo Global Logistics. As for being outed as an almost-billionaire: "It's a good thing and a bad thing."

Ray R. Irani

Occidental Petroleum
Estimated net worth: $700 million
Angrier shareholders will cheer when Irani, the third-highest-paid U.S. CEO of the past decade, sets a future retirement date this fall. He'll still get paid like a prince for years. Irani's $600 million in Oxy shares could benefit from a potential 1-billion-barrel find near Bakersfield, Calif., and high oil prices.

James Cameron

Movies
Estimated net worth: $650 million
Avatar, the 3-D movie he directed, was a giant leap forward in cinematic special effects. It also earned $2.7 billion at the box office and is the bestselling Blu-ray disc of all time. His older films, including Titanic, have earned a combined $3 billion.

Michael Jordan

Basketball
Estimated net worth: $500 million
Former Chicago Bulls wonder earned $90 million in salary during his playing career. Most of his fortune now derives from endorsement deals with his biggest sponsor, Nike; he raised his stake in the NBA's Charlotte Bobcats to 80% this year.

Tiger Woods

Golf
Estimated net worth: $500 million
Assumes $130 million in career prize money and $900 million in revenue from endorsements, appearance fees and golf course design business since 1996. His agents, the tax man and recently divorced wife Elin Nordegren have all gotten pieces of those earnings. But he will make it to 10 figures if he starts winning again and sponsors return.

Jay-Z

Music
Estimated net worth: $450 million
Jay-Z has elevated hip-hop to rock arenas, packing ballparks with Eminem this summer. If he keeps selling out monster shows money will rain down on all his ventures: the Roc Nation label, a back catalog (ownership reverts to him in 2014), Rocawear clothing royalties, a stake in the New Jersey Nets. He'll score nicely if a suitor buys Carol's Daughter, a hot beauty care line backed by Jay-Z and other celebs. He and wife Beyoncé Knowles may already be music's first billion-dollar couple.

Craig Newmark

Craigslist
Estimated net worth: $400 million
Newmark started e-mailing friends a list of San Francisco events in 1995. It became the basis of Craigslist, the Internet's most popular classified ad site. While most of the listings are free, it does charge for job postings in 18 cities and brokered apartments in New York. The site was pressured to shut down its sex ads section, another money-maker, in September. Analysts figure the site, which is available in 70 countries and gets more than 20 billion page views per month, could be worth $3 billion if it charged for postings in all cities, ran ads and cleaned up listings

Tyler Perry

Movies, TV
Estimated net worth: $350 million
Perry writes, directs and stars in his work (which has a huge audience with black Americans), owns his two TBS sitcoms (House of Payne and Meet the Browns) and negotiates a cut of his movies' earnings. He opened his own studio in 2008 and recently purchased a 58-acre estate in the Atlanta area for $7.6 million.