Gizmo 4

Gizmo offers free software and free calls to all other Gizmo users. The interface is very user-friendly and the company claims it "is as simple as instant messaging". A bonus to this service is the "All Calls Free" plan, which states that Gizmo users can call other Gizmo users' landlines and mobile phones, not just their computers. But, be careful to follow the company guidelines to avoid possible charges.