Check out Talkatone. I have it and love it. Using (a good) wifi, you can call from ANY COUNTRY in the world to any phone, land or cell in the U.S. or Canada. You get 10 free minutes a month with 60 minutes for only 99 cents if you need more time in that month.
I think (but am not 100% certain) that you can call anyone from anywhere to anyone anywhere if the other person has Talkatone as well. You get to pick your phone number among a list. You must keep it active or you lose your number and must pick a new one if you want to use Talkatone again. BY active I mean one phone call a month no matter how short it is.
Any unused minutes carry over to the next month.