I'm not a big fan of Apple products.  I had a particularly bad experience with an iPod I bought for my trip to Thailand in 2008.  While I have to admit, it was nice to have something I could watch American news broadcasts and TV on in my free time, the user interface was so poorly designed and implemented that I decided to sell it once I got back to Hawaii.

Despite my firm stance that Apple interfaces are often good ideas that don't end up scaling very well, I do happen to like Apple's concept of the dock.  By default, Ubuntu comes installed with two panels, one at the top of the screen and one at the bottom.

Example of the Ubuntu 9.10 Desktop

The one at the top has drop-down menus for your applications and utilities and also the date, time, network status, volume, etc.   The one at the bottom behaves like your standard Windows taskbar.  Each running program is represented by a horizontal bar with the application's logo and some kind of title.  Apple's dock concept is, in my opinion, superior.

Example of an Apple OSX Desktop with a Dock

On the dock, each application is represented solely by its icon.  The icons grow larger given their proximity to the mouse.  They also remain on the dock regardless of whether or not the application is currently open.  If it is open, a light below the icon tells you as much.

While Ubuntu doesn't come with any pre-installed dock, there are three that I've tried.  Here's my experience with all three:

1. Avant Window Navigator — I honestly don't have the most up-to-date information on Avant.  I first used this utility about six months ago, so my information may be out of date.  I installed Avant Window Navigator in Ubuntu 9.04 from the "Add/Remove Software" tool.  In Ubuntu 9.10 it's still available.  The user interface was very intuitive.  It was easy to get AWN to look the way I wanted it to.  I ran into some problems with screen "real estate."  AWN wanted to reserve a place at the bottom of the screen for itself.  I found the "invisible boundary this created for maximized windows off-putting.  It didn't feel right to have my desktop background showing through the dock after maximizing a window.  The option existed to nix the dock's reserved space, but then the problem became that the dock tools would sometimes be on top of some useful tool at the bottom of my maximized window.  Frustrating indeed.  In the end, this issue, combined with a pretty heavy memory overhead (at least by Linux standards) made me give up AWN.
2. GnomeDo's "Docky" Mode — I had already been using GnomeDo for awhile when I gave up AWN.  GnomeDo allows you to quickly find files, launch applications, and much more with one simple hotkey combination: Super+Space.  It remembers what programs and files you open, so while you may have to type "f-i-r-e" the first time to get Firefox, by the fifth or sixth time, it'll be the first option under "f".  When I began to search for a new dock, I was surprised to discover that the utility I'd been using for months in "Classic" mode also contained a dock toolbar mode called "Docky".  You simply go into the preferences for GnomeDo, found under the arrow menu after opening the program with Super+Space, and switch modes.  The dock will appear at the bottom of the screen.  From here, it's as easy as dragging and dropping items from the Applications menu onto your dock.  Even better, there's an "intellihide" feature that will hide the dock automatically if any window moves over the dock area.  The dock will reappear despite that if you move your mouse to the bottom of the screen.  Very clever.  Low memory footprint too.  Not much greater than what GnomeDo was already using in Classic mode (and that was very minimal).  GnomeDo is also available to install from the Ubuntu Software Center in version 9.10.
3. Cairo Dock — I discovered Cairo Dock two days ago.  It is much like Docky, except with slighly higher resource consumption than Docky.  However, the trade-off was worth it.  For those extra resources, you get oodles of customization options, screenlets (which aren't my thing, but others many like them), dock plugins, themability and community themes availability and all the same functionality as Docky.  My one complaint has to be that Cairo will hide my dock even when a window isn't over the dock area.  The only way to make the dock visible is to move the mouse pointer down to the bottom of the screen.  However, this isn't quite such a big deal.  The dock doesn't really need to be there when my mouse isn't at the bottom the screen.  It just needs to be there when I want it there and hidden at other times.

I think eventually Ubuntu may end up incorporating something like this into the default Ubuntu build.  There still seems to be a bit of redundancy.  The dock bar and GnomeDo together basically render my applications menu redundant — so long as I can remember the name of the application I want to run!  I think someone will come up with a smart, intuitive and sexy way of putting this all together in the future.  Until then, I'll be sticking with my dock.