Has your OS X menubar, Dock or Finder crashed? These very simple Terminal commands should do the trick, at least in version 10.8.3 as of 23 May 2013.
If you find yourself in those situations, just start up Terminal (hint: just type it in Spotlight and press Enter), and issue the appropriate command.
… or, Ctrl-Option-Click the Finder icon in the Dock.
So try this if you’re running OS X and find yourself with a crashed Finder, Dock or Menubar, so you can get started again quickly without a reboot.