A new VOIP application in Viber, developed by iMesh promises to one up Skype not only by allowing calls over 3G and Wi-Fi but by also integrating with your contact list, denoting other Viber users and allowing invites for non-users. The app also integrates with the dialer app, so that when a Viber call is received, you only need to pick up the call as normal and the call is routed over 3G. Future plans include Android and Blackberry versions along with SMS support.
Both the app and service are completely free for the time being with no advertisements of any kind and is available from the iTunes App Store.
If it turns my Sprint Galaxy Tab (Android version) into a phone, Skype gets kicked to the curb!