If you frequently run multiple programs simultaneously, your desktop can get extremely cluttered. This can get annoying if you're working on one program and want to minimize all the other windows -- in previous versions of Windows you had to minimize them individually.
With Windows 7's "shake" feature, though, you can minimize every window except the one in which you're currently working -- in a single step. Click and hold the title bar of the window you want to keep on the desktop; while still holding the title bar, shake it quickly back and forth until all of the other windows minimize to the taskbar. Then let go. To make them return, shake the title bar again.