Google has extended its free Gmail calling deal throughout 2012, offering free domestic calls for users in the US and Canada. The extension to the free service is the second since Google launched its VoIP integration in Gmail back in August 2010; US and Canadian domestic calls were included at the start as a promotion, and then kept on throughout this past year.
The VoIP system integrates with both the chat contacts list in Gmail as well as offering a regular dial pad to make calls to landlines and mobiles. Google also throws in $0.10 of credit for you to try out its paid calling plans.
Unfortunately those outside of North America will still have to pay for all of their calls, as Google is yet to extend the free deal. Still, Gmail voice calls are offered in dozens of countries, and support multiple simultaneous calls at the sort of low rates we've come to expect from VoIP. More details on tariffs here.