Minimize and Hide All Windows in Mac OS X with Command+Option+H+M
By combining the Hide All shortcut with the minimize keyboard shortcut in Mac OS X, you can use a third ‘Minimize and Hide All’ shortcut by hitting the Command+Option+H+M keys together.
The effect is instantaneous and immediately clears the display of any and all application windows, without closing or quitting any of the apps. As the title suggests, rather than closing anything, this keyboard shortcut will hide all other applications and windows, in addition to minimizing the currently active application or window into the Dock, effectively clearing the entire screen and giving you a blank view of the desktop on the Mac.
If you have Dock icon translucency enabled as shown in the screenshot, the hidden apps will appear as translucent. Meanwhile, the minimized windows from the foremost app will be in the Dock separately, on the right-hand side of the Dock as minimized windows appear as usual.
This works the same in just about every version of OS X tested, from Lion to Mavericks to Yosemite. Heads up to @sambrowne for the great little keyboard shortcut tip. If you have any little-known yet awesome keystrokes like this for OS X, let us know!