Haven't used cards in years. We love Vonage (VOIP at
www.vonage.com). It's very comfortable to use from any room and any telephone in our home so I prefer it. It's far more "stable" with fewer dropouts than MagicJack or Skype. Vonage is about $33 per month including taxes for unlimited long distance around the world. You can take a Vonage with you and set it up anywhere there is broadband internet and you can select any number you wish as there are no long distance charges.
Vonage also give the ability for "virtual" numbers from several countries. A UK number is just $5 monthly and a number in Poland is just $10 monthly. Both ring on our home phone.
However because my work requires communication redundancy we also have Skype in both locations (Moscow and USA) and Skype to Skype is free.