I noticed today that when Photoshop 7 is rendering, converting or doing anything which shows a progress bar, the bar is also displayed over the dock icon. Useful for watching progress as all the application windows disappear when Photoshop is in the background.
[Editor's note: Yes, this is a bit of a basic hint, but it hasn't been documented here before ... and if you're new to OS X, a good general hint is to keep an eye on your dock -- if you have apps doing stuff in the background, many of them will use the dock to update you on their progress (and for fun, try minimizing an iChat conversation window to the dock!).]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030117064217321