Hi Stephie,
If you can still find tomato and
pepper seedlings you should still have time to get some fruit from them(mine are doing better once it started getting hot). I would recommend cherry tomatoes since they seem (to me) to produce faster. Lettuce, radishes, cucumbers, and bush beans should be able to start from
seed.
With the lettuce, radishes, and beans you should be able to get a couple of crops done before frost. There are some good
seeds out there that do well in the heat and the fall.
You can increase the number of lettuce and radish crops by planting in the shade provided by your other veggies.
Good luck!
Shawn