If you’re like me, you dislike leaving your display(s) on when you leave your machine for an extended length of time. To turn them off, there are a number of options. You can set a short sleep timeout in the Energy Saver System Preferences panel, of course, but that gets annoying if you pause while working. You can also use Keychain Access (via its Preferences) to add a menu bar item that includes a Lock Screen function. Finally, using the Exposé & Spaces System Preferences panel—in 10.4 and 10.5—you can set one corner of your screen to Sleep Display. Drag the mouse to that corner, wait a second, and your displays will sleep.
In 10.5, though, there’s a hidden method—one that’s easier than all the others, I think, and requires no use of the mouse or menus. Just press Shift-Control-Eject, and all attached displays will instantly go to sleep. Move your mouse or press a key on the keyboard, and the displays will awake. It doesn’t get much simpler than that.
Note that this is not a secure display sleep mode—if you’ve set your system to require a password on wake from sleep or screen saver, it will not be triggered if you’ve slept your displays in this manner. You can make it secure by first starting the screen saver (probably by using a hot corner defined in the Exposé & Spaces System Preferences panel), then pressing Shift-Control-Eject. The password dialog will appear when you press the hot key combo, but if you then click Cancel, the displays should then go to sleep (they did here in my testing, at any rate).
Again, this will only work in 10.5, and if you’re not using an Apple-provided keyboard, it may or may not work. Also (somewhat logically), if you’re using
Caffeine to prevent your Mac from sleeping, this trick won’t work—the screens will go black, but then instantly awaken.