Remember Aero Peek, the feature that let you hover over the edge of the taskbar to show your desktop? That's still around in Windows 8, but you have to enable it first. Right-click on the taskbar, choose Properties, and under the Taskbar tab check "Use Peek to Preview the Desktop." You won't see the button at the right edge of the taskbar like you did in Windows 7, but it's there—just hover your mouse over the area right of the clock and your windows will turn invisible again. You can also click this area to show the desktop instead of just peeking at it.