Thanks, Ajulian. I knew about those Windows Key shortcuts; I was looking for the Taskbar Button.
However, looking at the "related threads" at the bottom of the screen I saw this thread, which sort of answers my question.
Show desktop?
Why'd they go and do a dumb thing like that?

I didn't even KNOW that thing was a button! It works, but it's far from the optimal location. I tried clicking and dragging it; doesn't work. Anyone know how to MOVE that "button that doesn't look like a button?"