The farmer’s market at Archives on Thursdays (8th St b/w D and E, I think) has a stand with “Scratch and Dents” for 99 cents a pound – I recommend using your goodies soon, but it’s a great deal. They usually have tomatoes and peaches, sometimes squash too. It’s a stand on the west side of the street closer to Teaism.
If you are canning, you can get deals through some of the CSAs – Lancaster has offered tomatoes and other produce in the past (firsts, though) and Orchard Country has offered deals on seconds but it just depends on what’s producing well that season. Good luck!