Brittany & Robbie Bergquist

Ages: 23 & 22
Hometown: Norwell, Mass.
Cause: Low-cost phone calls

At ages 12 and 13, after hearing about a soldier in Iraq who owed $8,000 for calls home, this sibling duo from Massachusetts emptied piggy banks and hit up friends to make a $21 donation. That effort snowballed into Cell Phones for Soldiers, a nonprofit that recycles phones to buy prepaid calling cards—over 210 million minutes' worth of talk so far—for soldiers overseas. In 2012, CPFS launched an effort called Helping Heroes Home, which assists veterans returning from overseas duty with one-time, emergency funding. So far, the group has given money to 2,500 vets and prevented an estimated 250 foreclosures.

Says Robbie Bergquist:

We've raised $7 million, but that first $21 was still the hardest."