At Rosa's Fresh Pizza in Philadelphia, the shop is adorned with Post-it notes and letters. The messages are from customers who gave $1 so homeless members in the community could get a slice, which costs $1. The pay-it-forward pizza program started about a year ago, [owner Mason] Wartman says, when one paying customer asked if he could buy a slice for a homeless person. I said, 'Sure.' I took his dollar and ran out and got some Post-it notes and put one up to signify that a slice was purchased," he recalls. Pay-it-forward pizza was born. Over the past nine months, Wartman says, clients have bought 8,400 slices of pizza for their homeless neighbors. He kept track of the prepaid slices with Post-it notes on the walls until he hit about 500 free slices. He now keeps track at the register. Wartman says the customer who started it all was inspired by a practice in Italy called "suspended coffee" where customers purchase an extra cup for someone who can't afford it. Pay-it-forward generosity isn't limited to Italian cafes or one Philly pizza shop. Even mega-chains, including the bakery and sandwich chain Panera, have gotten into the giving act. Other chains' pay-it-forward systems have grown organically. Starbucks Coffee Co. spokeswoman Sanja Gould says some people just offer to pay for the person behind them in line, while others "might load a certain dollar amount onto a Starbucks card and the store partners have it on hand and they keep adding to it as the line goes on." Wartman says ... people want to help but aren't sure what to do. "This is a super-easy way, a super-efficient way and a super-transparent way to help the homeless."