We take tomatoes for granted now, and it would be quite difficult to imagine Italian cuisine without them, but it took Italians a very long time to accept them: Though they were introduced as ornamental plants in the 1500s, the earliest evidence of their use in the kitchen comes from Francesco Gaudentio's Il Panunto Toscano, published in 1705.

A couple of observations on selecting tomatoes: Italians divide them into two classes: insalatari and da salsa.

Insalatari, as one might expect, are salad tomatoes, to be eaten raw. People generally select them not-too-ripe, in other words quite firm, with streaks of green running through them, and with a lively acidity that complements the flavor of the greens in the salad. Pomodori da salsa, on the other hand, are for cooking and should be ripe -- an explosive red, rich, and slightly sweet too.

These are Pomodori a grappolo, tomatoes sold by the bunch mostly destined towards salads, which are standard market fare, sun ripened in summer and (I expect) hothouse in winter.

More Italian Tomatoes:
Tomato Background, Info & Recipes
Insalata Caprese, Mozzarella and Tomato Salad
Riso con Basilico e Pomodori, Rice with Basil and Tomatoes

Tomatoes Elsewhere on About:
Bacon and Tomato Salad
Low Fat Three-Tomato Salad
Zesty Green Chile and Tomato Salad
Healthy Watermelon and Tomato Salad