http://www.pinger.com/content/int/
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A startup called Pinger says it has already built a big user base for Textfree — which is (you guessed it) a free text messaging service. Now it's offering a similar service for making phone calls. — The calls can be made over a 3G cellular data network or Wi-Fi.
http://venturebeat.com/2010/09/28/pinger-free-phone-calls/
:quote end