What is your favourite supper for a hot summer evening?
Other than ice cream? :)
Well, ok then. A fresh salad with delicious cheese and a vinagrette (like this Goat Cheese, Walnut, and Strawberry Salad) is always awesome, since there is no cooking involved whatsoever!
Aemmeleia's Ephemera 
I love Tortellini with Pesto in the summer. You can serve it hot or you can serve it cold. No matter how you have it, it tastes great.
Not sure if this counts, but I rather enjoy sliced (or diced) tomato with sliced (or diced) mozzarella cheese. Very simple and light.