Here is a tip that applies to any application that uses Microsoft's Fluent Interface, with the Ribbon and Application button. On my machine this includes Office, MindManager and Snagit.
Although it looks like a "button" the active area extends to the top left extent of the application. If the application is maximised don't bother carefully selecting the round button, just fling your mouse pointer to the top left corner of the screen and click to open the application menu.
Sadly it doesn't work with the Autodesk "clone" ribbon (left) which has a dead area above it's Application Button.
On standard windows applications (right) the same action will display the window menu.
UPDATE 2009-08-20: The AutoCAD 2010 Ribbon has an application button that matches Office!