Skype variant for Windows Phone 7 is a work in progress.

You probably remember sometime back, Skype announced that they had no
plans to develop Skype for Microsoft mobile platform. Well they
haven't change their mind for whatever reasons which we can imagine is
politically motivated. Fortunately, a developer over at Xda has
started working on a variant of Skype which for now allows for
chatting only. The project is still in progress and the developer is
looking for help in the design of the app. So, if you have time and
the skills, go to
http://forum.xda-developers.com/showthread.php?t=926939.

At this stage, contacts and ability to chat are working.

I have the feeling that Skype is not going to like this.