To show open windows...
wmctrl -l
wmctrl -lpG
Move the window to the current desktop, raise the window, and give it focus...
wmctrl -iR window
Temporarily prevents activation of the screensaver and power saving mode. Handy if you are doing something like playing music in Plexamp and you want the screen always visible so you know what's playing but you don't want to keep interacting via mouse/keyboard.
Generally used in conjunction with "Caffeine Indicator".