If you want VoIP with an actual phone number, for free, get a Gizmo5 number, attach it to a Google Voice account, and make calls connect through the google voice website, and you can take the calls over Gizmo5 or Fring.
Unlimited calls both ways, for free (only if you live in the USA though)
I used to do this with my Samsung Jack before someone stole it...from my locked room no less...while I was asleep...