Rahul Kohli of the CW's "iZombie" is one of many celebrities participating in the viral #15SecondShakespeare campaign to raise money for the Red Cross.
TV personality Star Jones is a heart disease survivor and American Heart Association national volunteer. Jones says she wears red every day in February to celebrate the association's Go Red for Women campaign.
Craig Pollard, left, started Cancer for College after battling back from cancer twice. The organization provides college scholarships to cancer survivors. Will Ferrell, Pollard's fraternity brother and friend, participates in the charity's annual fundraiser and is a champion for the cause.
Skier and U.S. Olympic gold medalist Bode Miller started the Turtle Ridge Foundation in 2005 as a way to help young people participate in sport and recreational activities. Miller also hosts an annual fundraiser, "Bodefest," at Cannon Mountain, New Hampshire.
In 2014, entertainer Nick Cannon served as grand marshal in the Lupus Foundation's Walk to End Lupus Now event. The singer was diagnosed with the disease in 2012 and works to raise awareness.
Seth Rogen raises awareness for Alzheimer's disease through the Hilarity for Charity comedy event. The variety show features performances by musicians, comedians and actors.
UNICEF Goodwill Ambassador Mia Farrow visited Central African Republic in 2013. Hundreds of thousands of people there were displaced because of conflict. Farrow helped create awareness for supplies that were desperately needed.
Demi Lovato is the ambassador for Secret's "Mean Stinks" campaign, which aims to end girl-on-girl bullying.
Actress Kristen Bell says she was alarmed to learn that hundreds of millions of people don't have access to clean water, so she found an unusual way to help. For her 30th birthday, she partnered with Charity Water and asked friends and family to donate money to the group instead of giving her presents.
Singer Reba McEntire hosted the 20th anniversary of Muhammad Ali's Celebrity Fight night, which raises money to help those with Parkinson's disease.
Designer Michael Kors has worked with his own foundation, Kors Cares, as well as with the U.N. World Food Programme to fight global hunger.
"This is something that's working." Actress Halle Berry visits a school in Nicaragua where the World Food Programme gives children a good meal and the opportunity to learn.
Jeff Bridges has worked with No Kid Hungry to help raise awareness for childhood hunger. The actor has campaigned on behalf of the organization's "Breakfast After the Bell" program in an effort to break the stigma of subsidized breakfasts.
Actress and UNICEF Ambassador Lucy Liu listens to the story of a refugee family at a cement factory in the Bekaa Valley in Lebanon. Liu has worked to highlight the plight of refugee children.
Country star Dierks Bentley started Miles and Music for Kids to help raise money for Vanderbilt Children's Hospital. An hourlong motorcycle ride that ends in downtown Nashville is followed by a star-studded concert.
Actress Alfre Woodard was friends with Nelson Mandela for more than 20 years. She credits the former South African leader with inspiring her to fight against apartheid and end the AIDs pandemic in South Africa.
As a United Nations "Messenger of Peace," actor George Clooney worked to highlight the plight of those caught in the crossfire of warring factions in Chad and what is now South Sudan.