If you've got a newer Mac--or perhaps just one of Apple's newer keyboards--you've probably noticed new newly-defined special function keys. For instance, while you can (on a laptop) still press and hold Fn and F9 to get Exposé's All Windows mode, it's much simpler to just press F3, the dedicated Exposé All Windows button.
But what about Exposé's two other modes, Application Windows and Show Desktop? At first, it seems you have to resort to using the old keys (F10 and F11, respectively) to activate those modes, complete with the Fn key gymnastics on a laptop. However, it turns out that Apple actually enabled these features on the new laptops and keyboards, but in a mostly-hidden manner.
To use Exposé's Application Windows mode, hold down the Control key, then press F3. Similarly, activate Show Desktop by holding down Command and then pressing F3. Finally, if you want to open the Exposé & Spaces System Preferences panel, hold down Option then press F3.
While this technique requires two key presses, there's still a big advantage on a laptop compared to using the older "Fn key plus the F9-F11 function keys" technique. With the old setup, unless you had the finger span of Shaquille O'Neal, activating the various Exposé modes required two hands--one for the Fn key, and the other for the appropriate function key. With Exposé now on the F3 key, however, it's easy to activate all of its modes with just one hand, even with the modifiers.
Unfortunately, you can't use the Exposé & Spaces System Preferences panel to change the default Exposé behavior of the F3 key by itself--it's hardwired to the All Windows mode. Even if you set the Show Desktop function to F3, for instance, you'll still get All Windows mode when you press F3.
Thanks to Mac OS X Hints reader Joseph Schneider for this tip.