Warren Buffett, CEO of Berkshire Hathaway, which owns MidAmerican Energy, the nation's leading utility in wind energy. It has invested $385 million to build wind-power plants.

At GE, CEO Jeff Immelt is betting that green technology will fuel the next century of growth. GE sold $10 billion worth of clean-energy gear last year and plans to put $3 billion into clean-energy ventures by 2008.

Cascade Investments, the investment arm of Microsoft Chairman Bill Gates, has invested in Pacific Ethanol, a public company that is building an ethanol plant in California.

Virgin Group CEO Richard Branson plans to invest up to $400 million in a biofuel plant. He is also investing in wind power and trains that run on biodiesel.

Microsoft co-founder Paul Allen has sunk $250,000 into Seattle's Imperium Renewables, which plans to supply 40% of the growing U.S. market for diesel fuel made from vegetable oil by 2009.

Vinod Khosla, co-founder of Sun Microsystems, is a biofuels evangelist. In the latest of a string of ethanol deals, Khosla Ventures and other investors are plowing $50 million into ethanol startup Altra.

Google co-founders Larry Page and Sergey Brin have invested in Palo Alto solar-energy startup NanoSolar.