Good info but I must remind everyone that there are already many VOIP providers providing this service for free not just to the US but to many other countries. It has better voice clarity(also depends on your connection speed), infact it's actually better than a cellphone call you make in India.
I use something called Internetcalls. It gives you 120days of free calling if you buy a $10 credit. And mind you that your credit doesn't expire after those 120days, you can use that credit to call after the 120 days where you will be charged at some 1cent per min. So in effect you are getting free calls for 120 days and cheapest calls after the 120 days..