Icon Tasks is modified KDE 4.7 taskbar applet that comes with some of the best Unity / DockBarX features. It supports Unity quicklists, counters and progress bars, window previews with media player controls, comes with DockManager API (you can use the Docky helpers in Icon Tasks) and lots more.
Here are a few screenshots:
|Window group - previews|
|Media player controls in tooltips|
|Unity progress bar|
Update: to get a Firefox support for Icon Tasks, install UnityFox 0.22 from HERE as well as "libunity6" package:
sudo apt-get install libunity6
Install Icon Tasks plasmoid
Ubuntu 11.10 Oneiric Ocelot users can install Icon Tasks KDE plasmoid from a PPA:
sudo add-apt-repository ppa:gnumdk/ppa sudo apt-get update sudo apt-get install plasma-widget-icon-tasks
For Arch Linux, get Icon Tasks via AUR.
Once installed, either remove the existing taskbar applet or create a new panel, right click it and select Add Widgets, then add "Icon-only Task Manager".
To use Docky helpers in Icon Tasks, install the following package:
sudo apt-get install python-dockmanager
Icon Tasks plasmoid comes with various options: you can change the style, preview window size, middle click behavior and lots more. To configure these, right click Icon Tasks on an empty space and select Icon-Only Taskmanager Settings:
For a complete list of features, source code, support and so on, check out Icon Tasks @ KDE-Apps.
Thanks to Luis Fernando Planella Gonzalez for the tip! Last 2 images via Icon Tasks @ KDE-Look.