I just noticed when I was trying to fool around with Spaces that by holding down Control and Shift, and then moving the mouse along the dock, the icons will magnify -- even if you have the Dock's magnification feature disabled. Pretty nice touch, if you ask me.
[robg adds: This shortcut isn't documented in either the general help for the Dock's keyboard shortcuts, nor in the Keyboard Shortcuts tab of the Keyboard & Mouse System Preferences panel. The icons will magnify based on the setting in the Magnification slider in the Dock System Preferences panel. So to change the magnification setting, enable magnification, change the slider, then disable magnification (assuming you don't want it on all the time).]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071026202623237