Leopard has Stacks to keep similar elements together on the Dock. For those of you that still have a hard time adjusting to this new feature, Quay brings hierarchical menus back to the Dock. Select an item or a folder as a base by dropping it on the Quay icon and then use that to launch your menu from.
Menus allow you to view the contents, sort the order of files or show only popular folders. You can also change the color and icon of a folder. A few users were put off by the fact that menus always pop up on the right, and hopefully in the next installment the developer will have allowed Quay to open up hierarchical menus on the left too. Clicking only once to open a menu also feels awkward at first but you quickly get used to it and it definitely speeds things up.
If you still find Stacks a bit awkward, set up Quay to bring back hierarchical menus to your Leopard Dock.