If you've ever used CandyBar before, you probably already grabbed version 3 when it was released the other day. But just in case you haven't seen it in action, Ged put together this great screencast of just how easy it makes controlling the look of your icons and Dock. I especially love the icons inside the iContainers in Quick Look-- such a neat, useful touch that's only possible in Leopard.
CandyBar, I think, is one of those apps that sounds like you'll never use it when you just read the text (because how often do you change your system icons, really), but once you see just how amazing it is, you can tell it's one of those reasons we're so proud to be Mac owners. I know, I sound like an infomercial, but look at that app! CandyBar 3 is available as a free 15-day/250-icon limit trial, or for the purchase price of $29.