Windows only : Freeware application Magic Boss Key hides your open windows (and desktop icons and taskbar, if you want) with a deft stroke of your keyboard or mouse. Magic Boss Key is sort of like the Windows-D/M keyboard shortcut except that it doesn’t just minimize the windows—it hides them entirely so that they don’t even show up in the taskbar. Hit the shortcut a second time and every window is restored to its previous state.
The software could improve tremendously if you could selectively choose which applications to hide (like Mac-only Show Desktop), since the only thing more conspicuous than a monitor full of non-work-related windows is one devoid of anything, but if your boss ain’t too quick on the uptake, this could do the trick.
Magic Boss Key is freeware, Windows only.