There are ATMs (known as bancomats) from various Italian banks located throughout Florence and Italy, including one on campus. In addition, there are ATMs practically everywhere in Europe, and most students find this to be the easiest way to get cash. However, before you leave, speak to your bank about (1) the high fees they may charge for overseas use and (2) not flagging your account as fraudulent due to the overseas use.
Western & Northern Europe: Used in most places.
Eastern & Southern Europe: Many places do not accept credit cards. Those that do more widely accept MasterCard and Visa than AMEX.