AOL and Yahoo will be making changes to the Free Voip features within their IM (instant message) services.

infoworld.com:

AOL
Eager to propagate the use of AIM’s Call Out service, which currently can only be accessed via PCs loaded with the AIM client software, AOL has released APIs (application programming interfaces) for this feature.

This Call Out feature lets people place calls to landlines and mobile phones from within the AIM interface for a fee to more than 200 countries. AIM also offers a free PC-to-PC voice chat feature called AIM Talk.

Yahoo
Yahoo has selected Jajah to provide the VoIP technology behind Yahoo Messenger’s premium voice service, which lets its about 97 million users make and receive calls to and from mobile phones and landlines in more than 200 countries.