EvaPhone is an online VoIP service that lets you make international phone calls for free thru your computer. All you need is a computer with Adobe Flash capability (which pretty much all the computers have these days) and a decent microphone headset. The call quality seem to be not that bad (given that it’s free). There is one catch, that it lets you make a certain number of free calls and then asks you to register and charge your account.
There is a chart on how many minutes of free calls are allowed for the list of countries that the service covers. Once those free minutes gets over then here are the rates for those countries. Looks like not bad of a service to try at least.