When you make a phone calls with google voice can be free and have rates in this 2010.
I have noticed for several days when i logged in into my gmail account to check my wordpress blog’s email, it has a message like “new! make phonecalls with gmail”.
If you live in USA and Canada, (Hawaii and Alaska are exceptions) you can call locally and internationally for free in 2010, also calling cellphones numbers. So don’t waste it! :) And i guess it will be charged in 2011. But i think it will be affordable as well.
If you want to call internationally, and want to know the “rates” you can always check the rates in: https://www.google.com/voice/rates