Windows Vista UI Guidelines Beta: How to design your next interface
Update: Better Office 12 interface link.
Microsoft has just published the beta version of their Windows Vista User Experience Guidelines (UX Guide). If you are in UI design phase for a new application. It seems prudent to align yourself with the new interface standards. It is also very important to take a very good look at the Office 12 UI, since it usually sets the precedent for User Experience expectations for other applications.