"Some boys like to play baseball, some boys like to play football. He likes to do charity work," explains Zach Bonner's mom, chuckling. In 2004, six-year-old Zach went door to door with his little red wagon to collect water for the victims of Hurricane...

Lower gaze. Quicken pace. Become absorbed in sight of sidewalk. In the hustle and bustle of city life, this is a common response to the sight of the homeless on the street. One day, a city-dweller breaks out of this routine when she stops to buy a...