I "leased" an incoming Skype number so my kids can call me while I'm on the island without enriching AT&T. With iOS4 the Skype app can be running in the background and the iPhone will ring with the distinctive Skype ring whether I'm on WiFi or 3G.
Yes, you can pick from various exchanges in your area code, or a number anyplace in the world for that matter. €5 a month for three months and then it expires.
I just logged on and reset by currency to USD. 3G isn't a very good choice as your roaming data plan will get nicked for the call. Sit in the villa and use WiFi.