Here is a list of useful time saving keyboard shortcut's for your Mac. These keyboard shortcuts for Mac OS X will save you time on your day-to-day tasks. They are for all versions of Mac OS X including 10.7 Lion.
General Application Shortcuts
Command Tab =
Switch between applications
Command H =
Hide application
Command Q =
Quit application
Command S =
Save
Command Option S =
Save As
Command O =
Open
Command X =
Cut
Command C =
Copy
Command V =
Paste
Command A =
Select All
Command Z =
Undo
Command Shift Z =
Redo
Command P =
Print
Screenshot Shortcuts
Command Shift 3 =
Capture screenshot of desktop to image file
Command Shift 4 =
Capture selection of desktop to image file
Command Shift Spacebar 4 =
Capture window to image file
Command Shift Control 3 =
Capture screenshot of desktop to clipboard
Command Shift Control 4 =
Capture selection of desktop to clipboard
Command Shift Control Spacebar 4 =
Capture window to clipboard
Apple Finder and General Shortcuts
Command N =
New finder window
Command W =
Close selected window
Command Option W =
Close all windows on desktop
Command F =
Search
Command Control N =
New Folder
Command L =
Make alias of selected application
Command I =
Show info of selected file
Command E =
Eject media
Command Shift H =
Open home folder
Command Shift A =
Open applications folder
Command Shift U =
Open utilities folder
Command Shift Delete =
Empty trash
Command Delete =
Move selected file to trash
Command Option D =
Show & hide dock
Command Spacebar =
Open & close Spotlight
Command Option Spacebar =
Open Spotlight in window
System Shortcuts
Control Eject =
Shutdown menu
Command Control Eject =
Restart computer
Command Option Control Eject =
Shutdown computer
Command Option Shift Esc (hold for 3 seconds) = Force quit current application
Command Option Esc =
Force quit menu
Control Shift Eject =
Put display on sleep mode
Command Option Eject =
Put computer on sleep mode