Free Unlimited Calls to 35 Countries via VoipWise. VW seems much more friendly at the first look. A download link on their homepage to get their VOIP softphone client is handy.
The following countries are included in FREE Calls promotion:
Canada, Czech Republic
Germany, Greece Greenland
Latvia, Liechtenstein, Luxembourg
Netherlands, New Zealand, Norway
Singapore, Slovak Republic, Slovenia, South Korea, Spain, Sweden, Switzerland
United Kingdom, United States (+mobile)