If you've gotten your new Windows Phone 8 device and are looking for the Windows Phone 8 version of the Skype app.... it's not out yet.
With Windows Phone 8, we are expecting some new features to Skype that include the ability to keep you signed-in and reachable even when you've closed out the Skype app. You'll also find that your Skype contacts are automatically added to your Peoples Hub and Live Tile support for unread messages.
When will Skype for Windows Phone 8 hit the shelves? Hopefully sooner than later
but in the meantime, you can use the existing version of Skype that can be found here (it's a freebie) at the Windows Phone Store. [Edit: Actually, George is incorrect here as you cannot run the old version of Skype on Windows Phone 8]