According to Rick, you can get prepaid SIMs from a mobile phone shop. However, I've heard elsewhere that you need to be a resident in Italy. Is it true? If not, have you had any hassles in getting prepaid SIM cards from TIM, Vodafone, or Wind?
I'd like to get a card that enables data access, since roaming charges are exorbitant on US carriers. TIM and Wind seem to have the best plans (500MB for EUR20). Has anyone gotten this? Does it work with 3G (UMTS)?