When one presses Alt key while in MS Word 2007 the shortcuts for all the commands are listed:
When one enters one of the tabs with the given shortcut, a next level of shortcuts are displayed:
I first saw this feature in Joel's FogBugz:
It's a really nice feature for the Ribbon (the new MS Office interface) to have. Great stuff, guys at MS.
Cons for Word 2007 Shortcut feature: some of the shortcuts are with
really strange letters, some of the things don't display shortcuts, for
example, some stuff in the status bar.