Mustard and small wild cherry tomatoes may naturalize. I grew the latter in TN and had them come back the next year. I've also scattered
mushrooms around the mulched/stick filled areas of my yard and had them make babies. Elderberries are a good forest edge species, as are sumacs. Rabbiteye and
native blueberries sometimes do well too. Horseradish, rhubarb, echinacea... lots of options. Great idea! You might also be surprised by what the birds plant. Black cherries, for instance, are all around the
fence lines here and the fruit is pretty darned good for a wild edible.
Also, since I'm on a "fruit
trees from seeds" kick right now... I'll mention this: you could go to your
local fruit stands and get their rotten fruit, then dump that around and see what happens. In the mountains of NC, I was on a property once that had a beautiful wild peach tree with wonderful fruit that was the likely the result of someone chucking a pit off a nearby porch. Peaches are supposed to be a bit tough to grow - but not this one. It was surrounded by wildflowers and growing in rich clay near a stream. Totally lovely accident.