Top 8 Tech Billionaires Who Dropped Out of College

The Microsoft co-founder and sports buff Paul Allen was ranked the most generous living American by the Chronicle of Philanthropy last year, endowing his family foundation with another $295 million. Since the foundation began in 1990, it has awarded $438 million, with 60% of funds going to organizations in Washington state. Allen's wealth is up thanks to rising Microsoft share price. His bet on redeveloping a downtrodden 60-acre parcel in Seattle's South Lake Union district continues to look smart as more condos go up and companies (Amazon) move in. Allen, a cancer survivor and autobiographer, gave another $70 million to the Allen Institute for Brain Science, which makes public a detailed "atlas" of genes that control the human brain. His science obsessions are taking him high and low: Allen teamed up again with aviation engineer Burt Rutan (they collaborated on SpaceShipOne) to build the largest aircraft ever built, capable of launching space-bound vehicles from the air. Test flights are planned for 2015. Allen also lent his personal deep-sea remote-operated vehicle to a survey of Coelecanth populations off the Comoros islands. He paid $25 million in September 2011 for another Manhattan apartment.