I just got a new Mac, and I'm enjoying its super-slim keyboard. While playing around with it, I discovered that pressing modifier keys while using the Exposé key you can produce different results. For example, it's well known that pressing Option and the brightness control (or sound control) keys brings up the appropriate System Preferences pane. Also, Shift and a sound control key will toggle between silent and beep on volume change.
But with the Exposé button you can do the following:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071114222901249