August 28, 2006—Most tennis stars do their charitable bit at hit-and-giggle exhibitions in cushy locales. Four-time Wimbledon champ Roger Federer, 25, who begins defending his U.S. Open crown today, has come out swinging for the kids of a South African township near his mom’s hometown of Port Elizabeth, a region with a 32% HIV infection rate. “Many of the children have HIV or lost parents to AIDS,” the Swiss superstar told POZ. “It’s important to give back and raise awareness about fighting AIDS.” Federer recently became a goodwill ambassador for UNICEF and vowed to take his children’s crusade global. Slam! —David Thorpe