Pizzas in Florence can't compete with their counterparts in Rome or Naples, but you can sample a few good approximations.
Baldovino (Via San Giuseppe 22/r, Santa Croce. 055/241773) makes pizzas to delight the kids and more sophisticated stuff to satisfy parents. In the Oltrarno, try Borgo Antico (Piazza S. Spirito 6/r, Santo Spirito. 055/210437), which serves pizza and other trattoria fare. The pizza at Il Pizziauolo (Via dei Macci 113/r, Santa Croce. 055/241171) is probably as close as you're going to get in Florence to the Rome and Naples versions. It has a thick crust, Naples style. The pizza con salsicce e friarielli (with sausage and a bitter green that's native around Naples) deserves respect. The pizziauoli (pizza-makers) successfully merge Roman (thin) crust with Neapolitan (thick) crust at Le Campane (Borgo La Croce 85-87/r, Santa Croce. 055/2341101). The Pizzeria Caffè Italiano (Via Isole delle Stinche 11/r, Santa Croce. 055/289368), a small pizzeria, is favored by locals. Come early to grab one of the few tables, and don't mind the fact that service here is intentionally rushed: turning tables is paramount. Pugi (Piazza San Marco 9/b, San Marco. 055/280981), which is handily across the street from San Marco, sells the popular pizza a taglio (pizza by the slice); their focaccie and other breads are equally good.