Source: snapvoip.blogspot.com

Yahoo has released a new version of the Yahoo! Messenger Release 3.0 (Beta 3) for MAC. The new version for Mac now has voice calling!. In addition to Voice (VoIP) capabilities, it also has;

Stealth settingsConferencing"New IM" indicator in the OS X dockTabbed conversationsMessage archivingStay connected from your mobile phoneAutomatic updates
The voice capabilities offer you chance to make free PC-to-PC calls (OK MAC to MAC Calls) or sign up for a Phone Out account to make calls from your Mac to regular or mobile phones worldwide for as low as 1¢ a minute (see rates). And if you want friends to be able to call you on your Mac from any phone, sign up for a Phone In account and choose a number. So overtaking all the tasks that you were doing with your phone.
The MAC could also use USB phones instead of Mic and speakers attached to your MAC. Just imagine the capabilities it offers your iMACs or MACBOOKs.
So how do I use these new voice feature? You’ll find a new “Voice & SMS” button in your IM window (see the graphic above). From there you can call another Yahoo friend, or send a free SMS (text) message to a friend’s mobile phone. And as we mentioned earlier, if you have Phone Out, you can also call anyones phone number directly from your MAC. If you also have the Phone In feature, anyone in the world will be able to call your MAC!
You can read more information at Yahoo Messenger Blog.