The software king is not the world's richest man, but that's because he is the most generous person on the planet: To date he has cut checks totaling $28 billion. (Even so, Gates is still America's richest person, topping The Forbes 400 for the 17th straight year.) Most of his donations have passed through his Bill & Melinda Gates Foundation, which now has a $33 billion endowment, including contributions from his buddy and bridge partner Warren Buffett. The foundation has given money for the prevention of 5 million deaths from AIDS, malaria and tuberculosis; now it's undertaking the eradication of polio. It is also fighting hunger by helping 400,000 farmers in Asia and Africa with rice varieties that resist cold, flooding and drought, and by giving 100,000 farmers on those two continents access to small-scale and cheap irrigation systems. As the foundation accelerates, Microsoft is stuck in neutral. Gates' stake in the company he cofounded is now worth $16 billion; its stock is flat over the last year, despite the release of a new Windows operating system and heavy investments in online advertising and games. Gates regularly sells shares in the software giant, pouring proceeds into investment outfit Cascade, which accounts for 70% of his wealth. Other investments include trash-collector Republic Services, investment firm Gamco, AutoNation and an inflation-hedging fund.