Google voice recently updated its availability for more countries with varying in call rates. I hope its been around more than a year of its announcement in US and Canada.
Now Google voice has been enabled for almost all the accounts. Call rates are affordable when comparing to local service providers and the best thing is making calls between US and Canada is completely free.

Google voice has updated about their call rates, as per Google voice features there is a number portability but which is not available for all the Google voice accounts. If you haven’t enabled Google Voice into your Gmail account visit Google Voice web page to enable it. If you are working in IT sector and if you have access to United States IP address via VPN then you can make free calls to US and Canada.
(Note : As the call rates are calculated in USD by default, hence you need to recharge by adding credits via your Credit Card or Google Checkout )