Earlier this year at the World Economic Forum, actor Matt Damon was presented with the Crystal Award for his social, environmental and humanitarian work, especially his efforts as co-founder of Water.org, a non profit organisation whose motto is "safe water and the dignity of a toilet for all".
He told the audience that Water.org is extending "water credit" to poor families so they can afford to install a toilet or connect their homes to a waterline that for them is "literally a lifeline".
The organisation has already helped more than five million people, and Damon said that it is estimated they could reach 100 million people by 2020.
Seven-time Grammy award-winning musician Will.i.am is determined that the LA ghetto he grew up in doesn't become a wasteland of disenfranchised youth. So he raised $7 million to start a STEM centre - science, technology, engineering and mathematics - aimed at upskilling young people and giving them a springboard for further education. Since then, and many projects later, he has worked with NASA to inspire youth to take an interest in technology.
U2's front man Bono is a well-known veteran of celebrity activism, and was picked out by the National Journal as "the most politically effective celebrity of all time". In 1985 Bono performed at Live Aid. This was the seed that saw him travel to Ethiopia with his wife Ali to spend several weeks helping with a famine relief project, an experience that shocked Bono deeply and ignited a determination that "where you live should not determine if you live".
Today Bono's advocacy and campaign organisation ONE has more than three million members who pressure politicians around the world to improve policies that empower the poorest.
Thanks to these efforts, along with those of partners and grassroots leaders in Africa, these policies have delivered exceptional results. In Bono's TED Talk last year he gave an overview of the last two decades in the fight against extreme poverty.
A self-proclaimed "factivist", he put huge points on the board with jaw-dropping stats. The global mortality rate of children under five has fallen so much that at least 7000 fewer children are dying per day. The number of people living in extreme poverty - making US$1.25 or less per day - has fallen from 48 per cent in 1990 to 21 per cent in 2010. And if the poverty rate continues to decline at the same pace it will reach zero by 2030.
Bono is a hard act to follow but one activist that has carved a unique path, that leads all the way from war-torn refugee camps in Southeast Asia to politicians on Capitol Hill, is actress Angelina Jolie.
Her interest in humanitarian affairs was sparked while filming Tomb Raider in Cambodia in 2000. She approached UN officials with the intent to help, but was concerned that her bad girl image might get in the way, and so they sent her to paparazzi-free zones in Sierra Leone and Tanzania.
In 2001 she was appointed Goodwill Ambassador by the United Nations High Commissioner, and since her appointment she has carried out at least 40 field missions in more than 30 countries that include Syria, Bosnia, Thailand, Pakistan, Iraq, Haiti, Ethiopia and Nigeria.
Angelina Jolie's film-making days may be numbered, declaring on numerous occasions that she finds her humanitarian work with the United Nations far more rewarding than standing in front of a camera.
She devotes one third of her income to savings, one third to living expenses, and one third to charity. Her donations to UNHCR have amounted to more than US$5 million since 2001. The funds have gone towards building schools in locations such as Kenya and Afghanistan, as well as programmes aimed at improving the lives of the forcibly displaced.
Jolie lobbies on behalf of orphans with AIDS, children without access to education, and alien minors without access to legal assistance.
"In my early twenties I was fighting with myself," Jolie has said. "Now I take that punk in me to Washington, and I fight for something important."
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