A very skilful person has created an ultimate screen saver, using the Bad Apple!! Shadow Art video. Since the video is black and white, he, supposedly he, made use of that to create a very interesting effect. The white parts of the video are actually transparent and show your current working layout, while the black parts are just black. You can get it here. The password for download is: BadApple. And there’s a step by step on mangajet.com.
btw. You need .NET Framework 4 to be able to install this screen saver.
EDIT: The download link seems to be dead so you can get it here.