I don't know anyone overseas to try this out, but this site says that they will give you free calls from the US to
Argentina, Australia, Belgium, Brazil (Rio De Janerio), Canada, China, Christmas & Coco’s Island, Cyprus, Denmark, France, Germany, Greece, Hungary, Ireland, Israel, Italy, Mexico, Netherlands, Norway, Poland (Warsaw), Portugal, Russia, Singapore, South Korea, Spain, Sweden, Switzerland, Thailand, UK and USA.
To use it, you call 712-858-8094, then dial the number you want to call.
No Limit On Call Length
Call from Anywhere, Anytimehttp://www.allfreecalls.net/
Here is the blog associated with the site: http://blog.roam4free.ie