If you are a Mac user who has grown to appreciate the dock functionality, Vincent Danen recommends the shareware app called DragThing, which allows you to do much more with the dock and customize it to your liking.
The OS X Dock is one of those things I can't decide if I love or hate. It's moderately useful, particularly in 10.5 and later which featured Stacks: a means to expand and view the contents of your Applications, Documents, and Downloads folders. But the Dock is still primarily an application launcher and rudimentary application switcher, with very little customization potential beyond resizing and repositioning it. As well, the Dock only allows you to store applications, not any other type of file, unless it is in a Stacks folder.
For a more versatile Dock, look to DragThing. This little shareware gem is a different kind of Dock for OS X that lets you have as many docks as you want, with different themes and styles, and also lets you store any type of content that you like.
For instance, I have a lot of virtual machines. I work with different operating systems, so I use DragThing to have a dock specifically to reference their virtual machines. This dock auto-hides, so it is tucked away at the top of the screen, and when it is moused over, expands to show its contents. With this dock, VMware files that make up the specific virtual machine are placed into the appropriate tab of the dock, so when any tab is moused over, I can quickly choose which virtual machine I want to load, double-click it, and have VMware launch it.
Creating a dock is easy. Open DragThing and select File | New Dock | Default. This will create a new floating DragThing dock. You can drag this new Dock wherever you like; if dragged close to the edge of the screen, it will snap to it. To have a minimizing dock, turn the dock into a drawer by going to the Drawer section of the dock's preferences. In the Appearance section you can change the dock's theme; there are a number to choose from.
The preferences have a number of options you can change -- many are for the appearance of the dock (DragThing offers a lot of options with how the dock looks), and some are functional: how many clicks required to open an item, position locking, and so on.
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Right-clicking on the dock itself offers even more ways to customize it. Here you can change colors, sizes, how to view the dock (text, icon sizes), arranging items by criteria such as name or label, change layer options, and so on.
Layer support is nice. This allows one dock to have multiple tabs (DragThing calls these Layers). By default the tabs are not visible, so you need to enable Show Layer Folder Tabs in the dock preferences, in the General section.
Each dock has a number of rows and columns, and this is where you can place the files you wish to use. Right-clicking allows you to add more rows or columns to the dock, so you can put more stuff in it. Unlike the Applications stack in the OS X Dock, which shows everything in the Applications folder, you can create docks for your most-used or favourite applications, commonly-used files or spreadsheets, and so on. Placing a folder in the dock will open the Finder with that folder when accessed.
DragThing also comes with special docks. The first is the Process Dock, which shows a list of all running programs, similar to the OS X Dock. Unlike the OS X Dock, you can position and customize this all you like. The next is the Disk Dock which shows you the physical disks on the system, and the last is the window Dock, which displays all open windows on the desktop. These docks can be accessed via the Window menu option of the DragThing menubar.
Docks can be only be dragged by their title bar, so by toggling the Show Window Title Bar option to off in the
General tab of the dock preferences, you can pin a dock to the desktop wherever you like and it will not move. This is a nice way to pin an often-used dock to the corner of the desktop, always visible.
DragThing is really nice software that I've used for years. It makes a great alternative to the OS X Dock and offers a lot of options and customizability that really make it useful for more than just application launching. If the OS X Dock is getting you down, or you want multiple docks or specialized docks, give DragThing a try.