CandyBar allows you to customize icons in your Dock. Note that although you can customise icons individually, you can no longer customize the entire dock in Mountain Lion OS X 10.8 due to a change in the way that Mountain Lion renders the Dock. As a result, the developers made it free of charge.
Panic and Iconfactory are both trusted developers on the Mac scene, the first for great software like Transmit or Unison and the second for the great icons they make. CandyBar is also an excellent app in the same vein as the others.
With CandyBar, you can create smart lists, drag and drop icons and select whole collections or unique icons. Icons appear in a dark transparent window and you can zoom in or out of them thanks to the slider on the bottom right of the interface. If you don't like the look of an Icon, you can make it look the way you want by simply dragging images in to replace them.
CandyBar 3 also includes a fully-featured icon organizer (formerly called Pixadex) that acts like iPhoto for your icons: you can collect and store your icons in the same application you use to change them. In addition, there's support for 512 x 512 icon support and Quick Look integration.
Note that although CandyBar is now free it will be virtually unsupported in the future apart from a few minor updates. The developers Panic have provided the following serial number: PPQA-YAMA-E3KP-VHXG-B6AL-L to activate CandyBar.
The only little drawback is that CandyBar doesn't offer a read me document or any advice for first time users who lack any knowledge of icon management.
Overall, CandyBar is a full featured tool to collect and organize large collections of custom icons for Mac.
