DialAdvantage is a prepaid long distance phone service offering up to 20 free minutes from USA, Calling to some countries may net less than 20 free minutes for your free trial.
Click here to activate a standard account & receive free minutes as a bonus.
Please note that Credit card not required for free trial, However your account will be processed in a similar way and needs activation after call confirmation from dialadvantage customer support.
I do not think its the best or cheap service for regular use, but you can always use the free trial minutes given by the companies. If you want a regular plan, I would request you to try Stanacard
I could not try this service, because I could not verify my account as I am not in USA. Leaving positive/negative comment after trying this service would be appreciated to help other readers.