Microsoft Office has a way to minimize and restore the Ribbon quickly. You simply double click the currently selected menu tab to toggle. As an example, for the picture blow, you would double click the Home menu to minimize.
In addition, using the ALT key triggers the ribbon to show the keyboard shortcut. This was obvious to anyone that frequently hit the ALT key by mistake. What I did not know, is that hitting the shortcut key will cascade down to the next set of menu. This even works if you have the ribbon minimized. Very neat!
Source: Double-Click a Tab to Shrink Microsoft Office's Ribbon Toolbar [Lifehacker]