That time of the year for free discarded plants!
Two of my nocturnal shopping spots - a well known smaller hardware store chain and a regional farm and home supply - ditch their remaining potted plants around the end of June. Last night I came home with 9 hanging baskets (everything from impatiens to dianthus) and about 3 dozen 3-4" pots including 13 Gerbera Daisies. Those retail for about $2.99 I think. Luckily the weather is unseasonably cool this week and I'll be able to get away with planting some of them even though it's late. Some will do well in porch pots or hanging as-is from the porch roof.
I also grab stacks of empty flats when I find them and donate them to a local nursery where I buy plants in the spring. I don't make anything off it but it keeps them out of the landfill.
Always take care when dumpster diving and leave the place cleaner than you found it.