Scarlett Johansson

Looking at actress Scarlett Johansson today, you'd never know she knew hunger as a child. But growing up in New York City, Johansson saw her parents work hard to put food on the table. "We were a single-income family with four kids living in New York City," she recalls. "My parents tried not to make a big deal of it, but I know it was a struggle for them."

One way Johansson's parents coped was by enrolling their children in government-subsidized lunch programs at their public schools. "It was the most practical thing for my parents," Johansson says."They could send us off and not worry." So when Stan Curtis, who directs the national food charity USA Harvest, approached her about working with a new program that provides kids in school lunch programs with weekend food, she jumped at the chance. Called Blessings in a Backpack, the program now donates food-filled backpacks to more than 27,000 children in more than 100 U.S. schools every Friday. "A lot of kids don't know where their next meal is coming from," Johansson says. "For parents to have some relief and know their kids are fed for those extra two days of the week, it makes a huge difference." (Read more about Scarlett Johansson.)

Stan Curtis

Twenty-three years ago, in a Louisville, Ky., cafeteria line, Stan Curtis watched a perfectly good pan of green beans replaced with a fresh one and then thrown away and thought, "Gee, I wonder if homeless people would like those green beans." With that, USA Harvest was born. His idea was simple: "We take food from people who have it and don't need it and give it to people who want it and don't have it," Curtis explains. All food is donated (USA Harvest operates with no annual budget) and delivered via groups -- shelters, missions, soup kitchens -- that help the less fortunate. Some 5,300 agencies operate in 130 cities across America, and with the help of 118,000 volunteers, two million meals are served each day.

To do even more for hungry kids, Curtis started Blessings in a Backpack, which distributes a weekend's worth of food in backpacks every Friday to public school children receiving federally funded meals. "The results are so astounding in terms of academics, self-esteem, attendance, and behavioral issues," Curtis says of his program. Still, he notes, "I would love to be out of business. That would mean people in America are not hungry, our school children are being paid attention to, and they have enough food to get an education."

Patricia Heaton/Mark Hyman

Mark Hyman, MD, is the parent of a child with tuberous sclerosis -- a condition that affects 50,000 people in the U.S. and causes tumors to form in the kidneys, eyes, brain, liver, and lungs, as well as seizures, autism, and learning disabilities. As such, he wants to see new research, better drugs and, ultimately, a cure -- and he knows all three take money. So seven years ago, the Los Angeles-based physician came up with an idea that made him smile. "I launched Comedy for a Cure," says Hyman, which takes place every year in cities across the country.

To make the event even funnier (and even more successful) Hyman enlisted his favorite patient -- funny lady Patricia Heaton of Everybody Loves Raymond and The Middle fame. The actress was MC at the Laugh Factory that first year and has donated her time to the cause ever since. To date their efforts have raised $2.5 million for the Tuberous Sclerosis Alliance. Those funds have kick-started research for genetic testing during pregnancy; sponsored a clinical trial for a new drug that may prevent and even halt tumor growth and seizures; and created the first national TS database, which centralizes information on TS patients. Progress like this is no joke.

Zane Gates, MD

When Zane Gates, M.D., finished medical school, he could have practiced anywhere. But he returned to his hometown of Altoona, PA, because he wanted to "pay a debt of gratitude" to the city and also follow his mother's tradition of community service. His free health clinic, Partnering for Health Services, allows him to do both. Ten years later, the clinic provides free health care to 3,500 of Blair County's working poor each year, thanks to an endowment by the Altoona Regional Health System and donations from the local community. "You can't put a price on good, hard-working people," Gates says. "Some of our patients say they'd be dead if we didn't have this program."

His model of care has attracted attention: The Pennsylvania Senate will soon vote on a bill that would fund clinics similar to Partnering for Health Services throughout the state. But the good doctor hasn't stopped there. Kids ages 4 to 12 living in two housing projects (one in which he grew up) can now attend after-school programs that he created through a foundation named after his mother, Gloria Gates. And as of October 2009, Blair County citizens can purchase a low-cost hospital-only insurance plan that Gates designed. His inspiration? "In this day and age, if my mother were living, she'd be one of the uninsured people in my clinic."