Windows logo key or Ctrl+Esc: Opens the Start menu from the taskbar.
Alt+Tab: Switches to the most recently used application window. Hold down Alt and press Tab more than once to move through the list. Add Shift to reverse the direction.
Alt+Esc: Switches keyboard focus to next application window on taskbar. Press Esc more than once to switch through successive windows. Add Shift to reverse the direction.
Move to next Excel worksheet: Ctrl+Page Up goes to the right; Ctrl+Page Down goes to the left.