Project Gizmo is a new Voice over IP application that seeks to challenge Skype, one of the best known free/fee Internet telephone applications. Project Gizmo is likely to win over the long run because the software is designed on an open source model that allows users to place calls to other voice software that uses the emerging SIP standard. Skype, by comparison, uses a proprietary protocol--you can only call other Skype users for free.
Both services charge a small fee of a few cents a minute to make connections to the "old" telephone network. The Gizmo software is available for both Windows and the Mac.
The big picture here is that traditional telephony is dead, dead, dead. One of the reasons the phone companies have resisted providing better broadband connections to users is their dread fear of losing telephone revenue. Cheap, fast fiber connections would encourage customers to quit paying for overpriced landline service and switch to VoIP.
The crazy thing is that this is already happening. The smart thing would be for the phone companies to simply compete--with better VoIP service. But instead, they are pouring hundreds of millions of dollars into lobbying efforts to keep the U.S. 16th in the world in broadband connectivity.