From TheFreeWindows:Each time you run the Activator it will minimize all inactive windows (the windows that are behind the one you currently work), letting you enjoy an absolutely clean environment, leaving only your recently active window over the wallpaper of your desktop. Activator is useful especially when you need to concentrate on your work.

Activator consumes no memory at all: it is invoked by a keyboard shortcut you can choose at will, and after it minimizes all inactive windows, it closes itself.