At age 28, Scott Harrison felt he had spent a decade of his life selfishly. For 10 years he had been promoting nightclubs and wanted to give back to the world. So he volunteered with a group that exposed him to poverty and disease around the globe. Most afflictions, he found, started with water. We would see people drinking from swamps and ponds and rivers, sources so unthinkable," said Harrison, now 38. "It seemed simple to attack the root cause by giving people clean water." He founded Charity: water in New York to tackle the world's water crisis after returning from a volunteer trip to Liberia in 2006. So far Charity: water has spent more than $55 million on more than 9,000 water projects in 20 countries, including Ethiopia, Rwanda and Malawi. Harrison recruits people to start their own fundraisers, and all of the money raised goes directly to the cause. Overhead costs are covered by "the well," which is made up of 100 donors who pledge anywhere from $24,000 to $2 million for three years. Well donors are largely Silicon Valley tech titans, like ... Matt Mullenweg, founder of Automattic, the San Francisco Web development platform behind Wordpress. "I've seen a lot of nonprofits and charities, and Charity: water continues to strike me as the most effective," Mullenweg said. "A dollar spent there goes a lot farther than anywhere else." Mullenweg has traveled to Ethiopia with Harrison twice since becoming a donor to "the well." "Every day was a rush of emotions and experiences," Mullenweg said. "We visited villages that didn't have wells yet and then those that did and it was night and day."