By FAR the best place in TO to get a calzone is Massimo's on College, just West of Spadina.
Absolutely divine. My mom used to bring some home for dinner every once in a while when I was growing up, and now that I work at the Clarke, I must eat there at least once a week.
THey make all their dough with spring water, and the ingredients are all fresh. Plus, if you want to stink like mad, you can spread a rough pesto all over your food.
They also make really good pizza slices for about 3.75, and a few pasta dishes and italian sandwiches.