Ok, apart from this... pizza should have his own topic for all its variants. There is "national" food from every region in Italy, so I'll mention some street food from my region for now.
Talking about "pizza" there's this variant, named
sfincione, it's not always a street food but...
...it's so common in my city that you can also find this funny guy wandering around shouting "sfincioneeee" and other slang words, which makes him amusing.
Then we have
panelle, made with chickpea flour, often with croquettes.
Although it's not street food, first thing that comes up in mind then is
caponata, mostlly because it's made also with eggplant, and I'm slightly allergic to it.
Few and not so elaborated dishes but enough for now, I'll post others later.