Yahoo is offering free group conference calling services from Vapps Inc. to the roughly 80 million users of Yahoo's instant-message and Web telephone-calling service, the companies said on Monday.

The service, called ConFreeCall, will be available for download through Yahoo Messenger with Voice service, allowing friends or families to hold free conference calls to complement Yahoo's existing text, voice and photo-sharing services.

Vapps, a supplier of conference-calling services and equipment announced a similar deal in June with Skype, the international market leader in instant message and Web-based phone calling services with more than 100 million users.

Vapps -- short for Voice over Internet Applications -- says it can offer free conference calls with high voice quality for up to 500 simultaneous participants per call -- enough to handle an extended family reunion.

A moderator can control call volume control, muting, announce participants and recording, among other features.

Closely held Vapps, of Hoboken, New Jersey, has a plan to offset the cost of providing free conference calls by offering related premium services, including conference call recording, playback and 24-hour operator support for arranging calls.

Yahoo Messenger with Voice subscribers can find the ConFreeCall application in the Yahoo Messenger plug-in gallery (http://us.gallery.yahoo.com/messenger). The service is also available directly from Vapps at http://www.confreecall.com.

Vapps counts tens of thousands of registered users for its existing audio conference call services. Previously it charged 6 cents a minute per user, meaning an hour-long conference call with 10 participants cost around $36.