Hold down the [alt] key and press the [tab] key.
a box will appear with all the windows on the lower toolbar displayed on it.
pressing [tab] again will move the selection to the next window
releasing [alt] will open up that window and bring it to the front of the pile.
the windows are displayed in the order last viewed, so the first one selected will be the last one viewed. A quick shortcut to switch windows without using the mouse!