2. Bill & Melinda Gates

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2. Bill & Melinda Gates

Microsoft co-founder

2004-08 Giving* $2,625 million

Bill and Melinda Gates give through their massive Seattle-based family foundation, which says it is "committed to ensuring all people have the opportunity to lead healthy, productive lives." With an endowment of nearly $36 billion, the foundation works with partners to give people a chance to lift themselves out of hunger and extreme poverty in developing countries and, in the U.S., to ensure that all people have the opportunities they need to succeed in school and life. Its endowment is eventually expected to double, thanks to a long-term $31 billion gift from investor Warren Buffett, which pays out in installments. Recent initiatives include $100 million in micro medical-research grants; a $164 million grant to the Alliance for a Green Revolution in Africa; and $125 million to fight global tobacco use as part of a $500 million partnership with New York City Mayor Michael Bloomberg.

For more, visit the Gates Foundation topic on Business Exchange.

*Based on public records and interviews with donors
Data: BusinessWeek, The Chronicle of Philanthropy and the Center on Philanthropy at Indiana University