An announcement today from Vapps, a company that provides the technology for free widespread conference calling over the Internet, confirmed that Yahoo's IM will get a group-focused "Messenger With Voice" service.

According to Yahoo, more than 80 million people worldwide currently use the IM's voice client on their computer. The new service, called ConFreeCall, will allow simultaneous conversations between as many as 500 people. Skype struck a similar deal with Vapps back in June.

The conference calling service will be available to all users free of charge. However, premium features, such as call recording and playback, as well as a 24-hour operator service, will be available for a fee. Previously, Vapps had charged 6 cents per minute per user for its existing conference calling applications.

Yahoo Messenger With Voice users will find the ConFreeCall enhancement as a plug-in for the messaging client. It can also be downloaded directly from Vapps's ConFreeCall Web site.

Voice-over IP is one of today's killer applications on the Internet. According to general estimates, more than 32 million households are expected to be part of the VoIP crowd by 2010.