If you want to go completely mono on your panel, Jan-Christoph Borchardt created 2 great mono themes for DockBarX: Mono-Dark and Mono-Light as well as a Minimal theme - which you can see in the screenshot below:

Talika is a GNOME panel applet that lets you switch between open windows using icons, similar to DockBar or DockBarX.

Talika .deb files are available, but not a PPA to stay up to date. Because I got lots of emails to create a PPA for Talika, here it is:

sudo add-apt-repository ppa:webupd8team/talika && sudo apt-get update

sudo apt-get install talika

And finally, add the Talika applet to a GNOME panel.

The PPA currently maintains Talika for Ubuntu 9.10 Karmic Koala, 10.04 Lucid Lynx and 10.10 Maverick Meerkat. Talika is also available in the WebUpd8 PPA - all the packages we maintain will also be available in the WebUpd8 PPA.

If you want to replace your Gnome panel with a dock, Avant Window Navigator (Docky also has a panel mode but only a few applets so it cannot fully replace a Gnome Panel) is no longer the only option as Cairo Dock 2.2.0 beta added a panel mode as well:

It appears the Humanity Panel Icons Pack has been updated, and now you can simply run a script to install all the icons (I wasn't awate of this, thanks rkv!).

Humanity Panel Icons pack includes the following icons: Printing, Shutter, Tomboy, Banshee, File Operations, Rhythmbox, Deluge, Fusion-Icon, Transmission, Gwibber, Emesene, Lifera, PolicyKit/Seahorse, Exaile, gPodder, Gwget, CellWriter, Gnome-Do, Specto, HPLIP, Brasero, Weather, Deskbar-Applet, Firefox. And more are expected.

One note: you MUST extract the downloaded archive inside your home folder, for the script to run.

Then, simply open a terminal and type:

./Humanity-Icons/Install_Humanity_Script.sh
or
./Humanity-Icons/Install_Humanity-Dark_Script.sh

Download Humanity Panel Icons Theme.

DockbarX, a taskbar with grouping and group manipulation with some "experimental" features compared to Docbark - great for replacing a Gnome panel, is now available for Ubuntu Karmic Koala. To install it, simply run the following commands in a terminal:

sudo add-apt-repository ppa:dockbar-main
sudo apt-get update && sudo apt-get install dockbarx 

Tint2 is a lightweight panel/taskbar intentionally made for Openbox3, but should also work with other window managers such as Gnome.

Tint2 features:

* panel with taskbar, systray, clock and battery status
* easy to customize : color/transparency on font, icon, border and background
* pager like capability : send task from one workspace to another, switch workspace
* multi-monitor capability : one panel per monitor, show task from current monitor
* customize mouse event
* window manager's menu

Tint2 is very configurable, like I told you above, but this is done via config files meaning you have to use a text editor for customizing basically... everything, which might confuse 'non-geeks', but we will cover a way to do all the configuring via a GUI tool, so keep reading.