Making Phone Calls Free VoIP On Gmail :

If you probably use Google tools to manage email, contacts, calendars, documents, etc.. but since last Wednesday to launch a new Google features. Google introduced the ability to make phone calls to landlines and mobile (GSM) directly from Gmail, in fact, Gmail users have been able to make voice and video chat pc to pc, but with this new feature, users can initiate VoIP calls directly from Gmail to any phone. Oh, I forget all the phone calls to the United States and Canada are free.
"More than 1 million calls are made from Gmail in the first 24 hours of launch VoIP service on gmail.
How to make free calls with Gmail?
All you have to do to get a call from gmail box and click the "Call" button that appears at the top of your Gmail contact list.

Gmail / Google Voice: Free Internet Phone :

Google Voice enables centralized telephone calls on a single number and free calls (in some cases).

Google Voice has many features: free phone call for national (paid abroad), send free SMS, divert calls to a landline or mobile messaging to a conversion of audio messages (telephone conversations or messages voice mail) in text emails ...

GrandCentral already allowed to make free telephone calls in fixed, mobile and VoIP on a single number. Voice adds the following features (not exhaustive):
- Transcription of audio conversations (Google Voicemail)
- Support for SMS
- Conference Call
- Integration of GOOG-411
- Low cost international calls (payment via Checkout)
- Integration with the Google Account and in particular to address book
- Block matching
- Recording of telephone conversations
- Consultation (old) transcribed telephone conversations via the Internet or by phone

So far Google has not been authorized by Apple to make available for iPhone Google Voice.