In 2000 Bill and Melinda Gates founded The Gates Foundation. As of writing it is 4x larger than the next largest charitable foundation in the US (Ford Foundation).
But the amount of money Bill and Melinda Gates are giving away is pennies compared to the charitable donations they have inspired.
In 2010 the Gates', along with Warren Buffett, organized a series of dinners amongst the United States' richest people. At their secret dinners they inspired a small group of billionaires to donate 50% of their wealth or more by the time they die. As of writing more than $365 billion has been pledged. To put that in perspective, consider that all charitable foundations in the US gave $53 billion in 2014.
The Gates Foundation is by far the largest private contributor in the fight against AIDS. Since 2005 -- roughly the same time that The Gates Foundation began donating large sums to AIDS research -- deaths from AIDS have fallen dramatically.
The Gates Foundation work to eradicate Malaria has been profound as well. Between 2007-2011 the foundation was the largest private source of AIDS R&D funding (25% of total funding).
He's also a DJ.