Yes, you can freeze squash slices.
Cukes- do you also have tomatoes? Cucumber tomato salad is yummy- especially with balsamic vinegar/olive oil dressing.
Or you can do those little silly cucumber sandwiches (you know, the things that show up at every bridal/baby shower ever that are basically cucumbers, cream cheese, and dill on bread?).
And I know a lot of people who use up their excess cucumbers by doing cucumber water.
We use extra cucumber as a simple headache/eyestrain remedy- just slices over your eyes while you lay back and rest a few minutes.
Peaches... You can definitely pre-make pies and cobblers and freeze them.
just make it up, but don't bake it. Then thaw before cooking.
They're also great to just freeze the sliced peaches all alone for use in things later. Frozen peaches are great for tossing into the blender instead of ice in a fruit smoothie. They're also great in oatmeal.