http://news.softpedia.com/news/Quick-Guide-Windows-8-New-Keyboard-Shortcuts-313374.shtml
Windows logo key + start typing - Search your PC
Ctrl + plus (+) or Ctrl + minus (-) - Zoom in or out of a large number of items, like apps pinned to the Start screen
Ctrl + scroll wheel - Zoom in or out of a large number of items, like apps pinned to the Start screen
Windows logo key + C - Open the charms / In an app, open the commands for the app
Windows logo key + F - Open the Search charm to search files
Windows logo key + H - Open the Share charm
Windows logo key + I - Open the Settings charm
Windows logo key + J - Switch the main app and snapped app
Windows logo key + K - Open the Devices charm
Windows logo key + O - Lock the screen orientation (portrait or landscape)
Windows logo key + Q - Open the Search charm to search apps
Windows logo key + W - Open the Search charm to search settings
Windows logo key + Z - Show the commands available in the app
Windows logo key + spacebar - Switch input language and keyboard layout
Windows logo key + Ctrl + spacebar - Change to a previously selected input
Windows logo key + Tab - Cycle through open apps (except desktop apps)
Windows logo key + Ctrl + Tab - Cycle through open apps (except desktop apps) and snap them as they are cycled
Windows logo key + Shift + Tab - Cycle through open apps (except desktop apps) in reverse order
Windows logo key + PgUp - Move the Start screen and apps to the monitor on the left (Apps in the desktop wont change monitors)
Windows logo key + PgDown - Move the Start screen and apps to the monitor on the right (Apps in the desktop wont change monitors)
Windows logo key + Shift + period (.) - Snaps an app to the left
Windows logo key + period (.) - Snaps an app to the right
Esc - Stop or exit the current task