Jeff Skoll, eBay President, First Employee
After becoming a billionaire at eBay, Skoll founded the Skoll Foundation in 1999, which focuses on "social entrepreneurship" to tackle problems around the world. The foundation has awarded more than $342 million over the past 12 years and funds a $20 million portfolio of program-related investments. Skoll also founded Participant Media, which seeks to inspire social change. Participant's films include "Syriana" and "An Inconvenient Truth."
In 2009, Skoll founded the Skoll Global Threats Fund, which focuses on climate change, water scarcity, pandemics, nuclear proliferation and Middle East conflict.
According to Forbes, Skoll -- with a net worth of $3.3 billion -- has donated $1.1 billion. Skoll was among the Giving Pledge's first signers.