WengoPhone

Free calls with a price

VoipBuster provides free calls - for a price. In what may be a mistranslation from the original German, VoipBuster advertises that if you buy credits, called "Freedays" you can then make up to 300 minutes per week of "free" calls to landlines in three dozen countries, plus mobiles in the U.S., New Zealand, Puerto Rico and Hong Kong. Go over that 300-minute limit, and you pay VoipBuster's normal rates, which are still quite cheap at 1.2 eurocents per minute including VAT.

Pro: Very cheap rates for toll calls.
Con: Confusing idea of "free."