Sheldon Adelson $15.3 billion Net Worth Increase In 2004: $13.5 billion Owner of the Strip's Venetian resort, who's now the king of Las Vegas. His net worth was up 750% in 2004 following mid-December public offering of Las Vegas Sands, making him the 11th-richest person in America. The stock is largely hyped on mogul's future: big plans for new casinos in Chinese gambling mecca Macau to go along with the Sands Macau casino (opened May 2004); and construction is under way on a Beverly Hills-themed mega-resort next to the Venetian. More On Sheldon Adelson >

Sergey Brin and Larry Page $7 billionNet Worth Increase In 2004: $6 billion In January, we figured the guys behind Google were only worth $1 billion. Oops. Since its long-anticipated, if wildly unconventional, public offering in August, Google shares have jumped 120%. At a recent $185, Google trades a rich 222 times trailing earnings. But with a combined net worth of $14 billion, it's unlikely Brin and Page are overly concerned. More On Sergey Brin > More On Larry Page >

Pierre Omidyar $13.4 billion Net Worth Increase In 2004: $5.6 billion Investors dumped eBay when the Internet bubble popped, even though its customer base continued to thrive. Bad call. Last year, eBay's online marketplace handled more than 1 billion transactions for 125 million registered users. The result: EBay stock is up 77% for the year, increasing Omidyar's wealth by $5.6 billion. More On Pierre Omidyar >

Kirk Kerkorian $8.1 billionNet Worth Increase In 2004: $3.1 billion Low-key investors hit the jackpot in June with a $7.9 billion takeover of Mandalay Bay Resorts. MGM-Mirage stock was up 83% in 2004, increasing Kerkorian's stake in the company to $5.6 billion and raising his total net worth 62% to $8.1 billion. He received $1 billion dividend payment from MGM before successfully unloading the studio for the third and final time--this time to a group of investors including Sony and Texas Pacific Group--for $5 billion. More On Kirk Kerkorian >

Michael Dell $15.9 billion Net Worth Increase In 2004: $2.1 billion The founder of the world's biggest PC maker stepped down as chief executive in July, but he's still reaping rewards from the surging customized PC business he started in his University of Texas dorm room. Company shares were up 23% in 2004; Dell's stake is now worth $11 billion. His increasingly diversified portfolio--including stakes in International House of Pancakes and Dollar Thrifty Automotive Group through MSD Capital--brings his total net worth to $15.9 billion. More On Michael Dell >

Warren Buffett $41.5 billionNet Worth Increase In 2004: $1.5 billion For a brief moment in April, Buffett challenged Bill Gates as the nation's richest man when shares of Berkshire Hathaway flirted with the $100,000 mark. Gates remains richer, but Buffett had the better year, tacking on $1.5 billion to his already formidable net worth. Buffett's latest bet: $20 billion against the dollar. More On Warren Buffett >

Edward Lampert $2.5 billionNet Worth Increase In 2004: $1 billion The hard-nosed chairman of ESL Investments orchestrated the $11.5 billion supermerger of Kmart Holdings and Sears Roebuck. His controlling stake in Kmart stock soared 310% in 2004, helping Lampert's personal net worth rise 67% to $2.5 billion. The protégé of Robert Rubin also holds a large stake in AutoZone and invests money for Forbes 400 members David Geffen and Michael Dell. More On Edward Lampert >

Stephen Wynn $2 billionNet Worth Increase In 2004: $1 billion The Vegas visionary's plush $2.7 billion Wynn Las Vegas mega-resort is near completion (opens April 2005). Wynn Resorts stock soared 147% in 2004 in anticipation of Wynn's return to Sin City--plus the hype surrounding his inevitable entrance into Chinese gambling locale Macau--putting an extra billion dollars in the mogul's pocket. With his vaunted art collection and additional proceeds from Kirk Kerkorian's buyout of Mirage Resorts in 2000, Wynn's net worth is now $2 billion. More On Stephen Wynn >

Martha Stewart $850 millionNet Worth Increase In 2004: $550 million She earns just pennies an hour toiling behind bars, but that hasn't stopped the imprisoned homemaker from cooking up a tasty fortune. Her shares of Martha Stewart Living Omnimedia are up nearly 180% for the year. That's enough to give Martha a net worth of $850 million--and a spot back on the Forbes 400. (Last appearance on the Forbes 400: 2001.) More On Martha Stewart >

Jeffrey Katzenberg $1 billionNet Worth Increase In 004: $200 million Talk about timing. A few months after their ogre flick Shrek 2 racked up nearly $900 million at the worldwide box office, the cartoon king and his billionaire partners David Geffen and Steven Spielberg spun off DreamWorks' animated division in a public offering. The November IPO gave DreamWorks Animation a market cap of nearly $4 billion and elevated Katzenberg into the billionaires club. More On Jeffrey Katzenberg >