We had earlier reported that Tango for Windows Phone would be launched soon. And here it is !
You can go get Tango here
The app looks for contacts in your contact list who have installed Tango and displays them in the list. It works with phones which don’t have a Front Facing Camera . Worked perfectly on my HTC HD7 .
So while Skype comes for Windows Phone, we suggest you try out Tango. It has a rich cross platform support ( iOs, Android , PC’s and Windows Phone )