To move to the next window or icon, press Alt+Tab or Alt+Esc.
To move to the previous window or icon, press Shift+Alt+Tab or Shift+Alt+Esc.
To shuffle through a stack of windows, press Alt+Up Arrow or Alt+Down Arrow.
To move between the windows belonging to an application, or the Front Panel and a subpanel, press Alt+F6 or Shift+Alt+F6.