Screen Capture to disk:

  ⌘ ⇧ 3                   Screen to jpeg file on desktop
  ⌘ ⇧ 4 + Drag:           Selection to jpeg file on desktop
  ⌘ ⇧ 4 + Spacebar:       Window (click camera) to jpeg file
Screen Capture to clipboard:

  ⌘ ⇧ 3 + Ctrl:           Screen to clipboard
  ⌘ ⇧ 4 + Drag + Ctrl:    Selection to clipboard
  ⌘ ⇧ 4 + Spacebar + Ctrl Window (Camera effect)
Dock /Switch Applications

  ⌘ ⌥ D      Show/Hide Dock
  ⌘ Tab      Switch applications
  ⌘ `        Switch between document Windows in current application
  ⌥ Dock     Switch application, hide previous one
  ⌘ Dock     Switch application, hide all others
 Ctrl ⌥ ⌘ *  Toggle Monochrome Hi Visibility
  ⌘ +drag will prevent dock icons from moving out of the way
             (useful for when dragging stuff to trash)
Apple Finder

  ⌥ + Drag   Explicit COPY (will copy even if destation is on same volume)
  ⌘ + Drag   Explicit MOVE (will move even if destation is on different volume)
  ⌘ ⌥ + Drag Make alias in new location
  ⌘ D        Duplicate
  ⌘ L        Make Alias
  ⌘ R        Show original
  ⌘ O        Open item
  ⌘ ↓        Open item
  ⌘ S        Save
  ⌘ ⇧ S      Save as
  ⌘ N        New Finder window
  ⌘ ⇧ N      New Folder
  ⌘ Q        Close Application
  ⌘ W        Close Window
  ⌘ ⌥ W      Close all Windows
  ⌘ I        Get Info
  ⌘ ⌥ I      Super Get Info (change whatever you click on)
  ⌘ P        Print
  ⌘ T        Add to Favorites
  ⌘ Delete   Move to Trash
  ⌘ E        Eject
  ⌘ F        Find
  ⌘ ~        Cycle finder windows (including desktop)
  Tab        Highlight next item
  ⌘ + double-click folder icon will open in new window
  ⌘ + ↑      Move up one directory
  ⌘ + [      go back
  ⌘ + ]      go forward
  ⌘ ⇧ A     Open Applications Folder
  ⌘ ⇧ U     Open Applications/Utilities/ Folder
  ⌘ ⇧ H     Open Home Folder
  ⌘ ⇧ K     Go to network
  ⌘ K        Connect to server
  ⌘ ⇧ G     Go to folder... (type full path)
  ⌘ ⇧ ⌫     Empty Trash (Finder Menu )
  ⌘ ⇧ ⌥ ⌫   Empty Trash without dialog

Finder-Hide App:
  ⌘ H        Hide Finder
  ⌘ ⌥ H      Hide Others

Hide all other apps*:
  ⌥ ⌘ + click on dock icon
  ⌥ ⌘ + click inside app window

Hide all other apps that are in front*:
  ⌥ + click dock icon (of running app)
  ⌥ + click inside app window

*Some older (pre-intel) apps may struggle with these
Terminal

  ⌘ left/right arrow   Switch windows
  ⌘ 1                  Switch to 1st terminal window
  ⌘ 2, ⌘ 3...          Switch to 2nd, 3rd window
Editing Text (email, TextEdit etc)

  ⌥ ←       Move one word left
  ⌥ →       Move one word right
  ⌘ ←       Beginning of line
  ⌘ →       End of line
            Scroll one page up (cursor retains position)
            Scroll one page down (cursor retains position)
  ⌥         Move one page up  (reposition cursor)
  ⌥         Move one page down
  ⌘ ↑ or   Scroll to beginning of document
  ⌘ ↓ or   Scroll to end of document

  Add shift key ⇧ to the above to also SELECT the text.

  ⌥ ⌫       Delete word  
  ⌥ Del     Delete next word

  ⌥ Scrollbar           Jump to exact scrollbar location
  ⌥ Scrollbar arrows    Scroll page at a time (page up/down)
  ⌥ Volume up/down      Open Sound preferences
  ⌥ Brightness up/down  Open Display preferences
Shutdown/Logoff:

  POWER         Sleep now
  POWER         Hold for 10 seconds (force shut down)  
  Ctrl Eject    Restart, Sleep, Shutdown dialog box
  ⌘ Ctrl Eject  Quit all applications and restart
  ⌘ ⌥+ctrl+eject Graceful Shutdown
  ⌘ ⌥ Eject     Sleep now
  ⌘ ⌥ + Esc     Force Quit
  ⌘ + .(period) Stop a process
  ⌘ Ctrl+power  Immediate restart (dangerous, only if system is frozen)
Log out:

  ⌘ ⇧ Q         Log out (Apple Menu)
  ⌘ ⇧ ⌥ Q       Log out immediately (Apple Menu)
During Startup:

  Shift      Safe Boot mode - Press shift asap AFTER the startup chime 
  ⌘ V        Start up in Verbose mode.
  ⌘ S        Start up in Single-User mode (command line)
  X          Force OS X startup
  ⌘ ⌥ ⇧ ⌫   Bypass primary startup volume (will seek DVD or external disk)
  C          Start up from a CD that has a system folder
  D          Start up from first partition
  N          Attempt to start up from a network server(NetBoot)
  R          Force PowerBook screen reset
  T          Start up in FireWire Target Disk mode
  ⌘ ⌥ P R   PRAM Reset - Hold down Cmd-Option-R with your left hand,
              then press POWER to start up and immediately press P with your right hand.
              See KB 2238  At the prompt you can  type: reset-nvram and/or reset-all 
  ⌘ ⌥ O F   Open Firmware
  ⌘ E        Eject CD (press during/after startup chime)
  mouse      Eject CD (hold mouse button down during startup)

OSX Keyboard Shortcuts

osx

Other