Here are some additional “hidden” uses of the PS3’s Power and Eject buttons.
Force a shutdown
Press and hold the Power button on the front of the PS3 for about 10 seconds to force the system to shutdown (safely).
Use this method if your PS3 freezes/crashes. Do not flick the power switch on the back of the unit to shutdown because it could potentially corrupt your files.
Force disk eject
Press and hold down the Eject button on the front of the PS3 for about 10 seconds to force the system’s drive to eject.
Useful for example if you try to launch a PS2 game and it freezes. You should be able to force eject the disc and then force shutdown the system.
Reset video settings
With your PS3 turned off, press and hold the Power button on the front of the PS3 for about 10 seconds (the system will beep as normal as it starts up but after 7-10 seconds it will beep again). The video settings should now be reverted. Doing this will also reset any theme settings.
I use this method to revert from HDMI 1080p to Composite 576p, without having to swap cables and change settings.