Now AIM messenger user can enjoy free phone services to call local phone number for free. i think AIM phoneline would be the first to offer a free phone number.
As i know, the user can pay 14.95USD per month upgrade their AIM phoneline to unlimtited accounts for calls to all local and long-distance numbers and 30 foreign countries. but still, this services still need a desktop or notebook just can call phone call through AIM software.

The AOL president also claim that AIM’s is more robust, with a phone number, 911 service and other features:

• It will be integrated with AIM and AOL e-mail. A dial-pad will drop down at the bottom of the AIM Buddy List. Voice mail, also free, will show up as an e-mail with a link to click to hear the message.
• AIM callers will get a reputation score. Users can click to tell the system if a caller is, say, an annoying telemarketer. That telemarketer will get a bad rep, which will show up whenever that caller dials. You can then choose to ignore the call.

As AOL company is coming this kind of free phone services, i think GoogleTalk, Yahoo and MSN for sure will counter attack AOL with more free services. i think the person that benefit will our internet surfer.