This is awesome!!
Yod'm 3D (Yet anOther Desktop Manager 3D): this little piece of software allows you to have virtual desktops with a 3D cube effect for the transitions. Note that it works on XP and Vista. It behave very well on my laptop and is not CPU consuming.
[edit: this is no more free...]
More info and download :
Someone to write this in WPF to have vectorial rendering and live preview during cube spinning ?