One of the nicest things about summer is the voluptuous bounty you'll find in a good vegetable market: Tomatoes, peppers, eggplant, zucchini flowers... Wonderful, and wonderfully refreshing. Some of my favorite summer recipes:
Very easy to do, and they add immeasurably to a cookout or picnic. What's more, if you make a big batch, you can enjoy them for several days.
Grilled eggplant is also nice!
Beautiful golden flowers from squash and zucchini, and to be honest many people enjoy them more than the squash or zucchini. I especially like them fried, though you'll also find links to stuffed zucchini recipes here.
These work nicely as an antipasto, and are wonderful as a main course when it's hot and other things would be too much. You'll also find a recipe for tomatoes stuffed with pasta here.
Very easy to do, and pleasingly zesty. Even those who object to eggplant eat it up.
This is a Spanish sweet-and-sour eggplant reicpe the Neapolitans appropriated and made their own. It's wonderfully refreshing on a hot day, and a big batch will keep for a week. Or so they say; I find it goes (much) faster.
Caponata, one of Sicily's signature dishes, involves eggplant and is usually baked; as you might guess there are many, many variations. This is a modern recipe, and also has tomatoes and bell peppers.
More traditional recipes also call for fish, sometimes quite a bit.
I know, beans are a legume, and not a vegetable, but freshly shelled cranberry beans have a delightfully nutty flavor, and are wonderful with a little onion, olive oil, salt and pepper. Served cool they'll revive you when the heat has done you in, and if you add some canned tuna you've got a fine meal too.
A big bowl of fresh, tasty chopped raw vegetables served with oil and vinegar that your guests can mix and season to taste in their own little bowls makes for a perfect antipasto or side dish.
I'm cheating here, because I like salad and the Romans are good at them. So the link leads to a selection of Roman salads -- more variety to choose from!
It's difficult to imagine summer without mixed boiled vegetables served cold. It's equally difficult to give a recipe, because there really isn't one: its composition depends upon what looks good in the produce section of the supermarket, or what the greengrocer has. In any case, if you make it in bulk, say a heaping salad bowl's worth, you'll have a refreshing side dish for several meals.
Though many people associate Italian cooking with pasta dishes and hearty soups of one kind or another, there's a very long tradition of making savory pies of the sort that the French might call a quiche. Nor is this surprising; they're quite tasty both hot and cool, and their being tasty cool makes them especially nice during the summer months.