Inspired by a cousin who lost the ability to walk and talk at age 3, Micaela Connery launched Unified Theater, a student-led drama club for all kids, disabled or not. Today, Unified Theater, which is being developed as an AmeriCorps program, works with thousands of kids at nearly two dozen schools; a spring production at Connery's alma mater, Conard High in West Hartford, Connecticut, featured a cast of 200. "This started in my cafeteria, as simple as it could be," says Connery, 23. "Anybody could do it." —Suzy Evans
In 1994, Jacqueline Murekatete turned 9, and her parents and six siblings were murdered in Rwanda's genocide. She got asylum in the U.S. and moved in with an uncle. As a teen, she began to speak out about the dangers of ethnic hatred. She raised funds to build a community center in her Rwandan hometown and created a curriculum to help prevent genocide. "I suffered through things that no human being should have to experience," she says, "and people need to know what happened." In December, she'll return to Rwanda for the first time since 1994. —John Dorman
When Will Perez graduated from high school, he was given six copies of Mountains Beyond Mountains, the story of Paul Farmer's efforts to transform Haitian health care. He took it as a sign. At Brown, he studied Creole and Haitian culture, and on the day after his graduation in 2008, flew to Haiti to fight tuberculosis. Reality changed his grand plans. "Our first program ended up being bedbugs," he says. "That's what everyone was complaining about." Now the Brown med student, 24, is devising public-health programs for the NGO Hope for Haiti. He helped lead his school's earthquake-relief effort and designed a Haiti — U.S. student-exchange program. Expanding access to health care, in Haiti and beyond, will be his life's work, he says, arguing that it's a human right "regardless of social status, regardless of economic status." —Rachel Arndt
Jessica Posner first ventured into Kibera, Africa's largest slum, as a Wesleyan University junior studying abroad in Kenya. Shortly afterward, she moved in, joining some 1.5 mil-lion residents in a community that Kenya's government considers an informal settlement (and therefore undeserving of public services). In the summer of 2009, she started Kibera's first and only tuition-free school for girls. She also founded a community center that serves as a clinic, library, and Internet access point, and is working on expanding access to clean water. "I'm lucky," says Posner, 24. "I made a choice to live in Kibera — everybody else there did not have that choice." —Austin Carr
In the fall of 2008, Mark Rembert got the good news: He had been accepted into the Peace Corps and was headed for Ecuador. Then he got some bad news: DHL, by far the biggest employer in his hometown of Wilmington, Ohio, was shutting down. So instead of going to South America, Rembert started Energize Clinton County, an initiative to create green jobs by encouraging investment in sustainable energy. ECC facilitates weatherization; has built coalitions of private and public partners; and has helped lure more than $1.3 million in funding to the area. "A lot of the principles used in the Peace Corps," says Rembert, 26, "were what was needed in Wilmington." —Emilie Luse
A version of this article appeared in the October 2010 issue of Fast Company magazine.