You can get a free VoIP phone number (also known as DID – Direct Inward Dialing) in Italy from Messagenet.it Receiving calls is free, and calls to other VoIP (SIP) users is free. Your account is rechargeable, allowing you to make outgoing calls to landlines or mobiles at rates cheaper than POTS services like Telecom Italia.
You can use it with software running on your computer (but you’d have to keep it running all the time, or else calls will go to voicemail and sent to your email as mp3). You can use it on your smartphone (they have apps for Symbian, iOS and Windows Mobile, but there are generic apps for Android, too). Or you can by a Linksys PAP2, attach it to your router and connect a regular phone to it. Here’s the configuration guide. Remember to forward ports 5060 and 5061 (both TCP and UDP) on your router.
You might also want to add a STUN server to facilitate NAT traversal: http://www.voip-info.org/wiki/view/STUN