Jenny,
As someone else mentioned, it's probably going to be less expensive to rent a phone here rather than in Italy. You might try one of the "travel phone" firms such as Roam Simple, Call In Europe, Cellular Abroad, Mobal or Telestial. They can not only supply phones but also SIM cards for those that have their own phone.
If you're planning on travelling on a regular basis, you could buy a phone from E-Bay or other sites and just purchase the SIM for travel. You'll need a quad-band, unlocked GSM Phone for use in Europe. I would suggest NOT using a "Smartphone" such as an I-Phone or Blackberry, as the data roaming charges can be horrendous. Also, not all "travel SIMS" support data service (although Roam Simple does offer Blackberry service, according to their website).
If you decide to purchase a travel Phone, be sure to check the Charger to make sure that it's designed for "world operation" from 100-240 VAC.
If you're just trying to set up meeting times with your friends, try to use text messaging as it's a lot cheaper!
Cheers!