Philadelphia's Rosa's Fresh Pizza might appear to be a regular pizza place, until you notice all the Post-its that line the walls. Each one represents a free slice, purchased by a customer and left for one of the city's homeless. All a hungry person has to do is come in, take a Post-it, and a free slice is theirs.
Founder Mason Wartman knows the idea is good for business (that's a lot of extra slices he's sold), and hopes to expand the model to other types of businesses soon. For now, as one customer says: "We're all eating the same pizza, and it's delicious."