I have a PowerBook G3 (Firewire) and found this keyboard shortcut just recently.
You don't have to go all the way to the Displays control panel to make Mac OS X detect displays, you can do it from the keyboard by pressing Command and BrightnessUp (F2). Saves time!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020326011328857