Voipbuster

Voipbuster is a competitor to Skype and the like. If you put 10 € into your account, you can call landlines in 32 countries and mobile phones in USA, Hong Kong and Puerto Rico for free for 120 days, with a limitation of 5 hours a week. A theorethical 85 hours in 120 days. That's a nice deal. Of course you can also make other calls, for a fee that usually is cheaper than Skype, with the 10 € you paid. Also after the 120 day period. Be aware, though, that calls are rounded up to next minute.