This story has gotten a lot of media attention, and I think it's important because it shows that people will gladly help others when you give them a fast, affordable and easy way to do it. Via NPR:

Some pizza restaurants decorate the walls with signed photos of minor local celebrities who once stopped by for a slice.

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 cost $1.

"The homeless, they come in and say, 'I hear you give out free pizza to homeless people,' " owner Mason Wartman tells The Salt.

The pay-it-forward pizza program started about a year ago, 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.

Over the last nine months, Wartman says clients have bought 8,400 slices of pizza for their homeless neighbors. He kept track of the pre-paid slices with post-it notes on the walls until he hit about 500 free slices. Then the accounting system became untenable. He now keeps track at the register.

But his customers — both paying and non-paying — keep sharing their motivations and their thanks in writing. On the post-it notes and papers hung around the shop there are messages like, "I just want to thank everyone that donated to Rosa's; it gave me a place to eat everyday and the opportunity to get back on my feet. I start a new job tomorrow!"

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.

[...] Wartman says the pay-it-forward method at his tiny Philly pizza shop has made him think about customers' motivations.

"They're just really nice people, you know? Sometimes homeless people buy them for other homeless people." He 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."

Wartman doesn't need to advertise, and he is receiving enough "paid forward" pizza that he does not have to turn away any of the homeless people who come in. He says word has spread within Philadelphia's homeless community and each day 30 to 40 homeless people come in asking for a free slice.