Its being reported on many sites that Skype have pulled its current Windows Mobile client due to 'sub-par' user experience. Understandable, Skype have never really got over the front speaker/back speaker issue within Windows Mobile and whilst its always been possible to fix it yourself using one of a few alternative audio re-directors, Skype's development team haven't really had the desire/know-how to deliver in an integrated way.
Apparently a new Skype for Windows Phone will arrive, probably for WP7S as the stronger controls over the hardware config will make it easier for Skype to deliver a seamless user experience. I'm told that the Java based Skype Lite client - incredibly useful for Android and WinMo users looking to take advantage of Three's Skype bundles - has also been pulled.
If you want Skype on your Windows Mobile device but don't have access to the install files you can retrieve them from here.