Mac OS X has some nifty shortcuts for hiding apps, useful when your boss or your partner is coming over while you’re doing ‘something’ on your Mac.
Use Command-H to instantly hide the app you’re currently using. The companion shortcut is Command-Option-H which hides all apps except for the one you’re currently using.
You can also use Command-M to minimize current window of the app you’re using. This is not as effective as Command-H as it is not instant. The companion shortcut key is Command-Option-M which minimize all windows of the app you’re currently using.
As a last resort, you can always press Command-Option-Shift-Q to logout immediately.