The extension provides numerous features, including the ability to move the panel to the top or bottom, change the panel size, live window previews, and more.

Avant Window Navigator is a dock / task manager for Linux, which was very popular a while back. Its developers lost interest with the introduction of Unity, and after several years of inactivity, the project was taken over by a new maintainer.

Unfortunately, the new maintainer isn't too active either, but at least Avant Window Navigator was updated to work with recent Linux distributions.

Mike Baum created an Avant Window Navigator PPA for Ubuntu 16.04 / Linux Mint 18, because the official AWN PPA wasn't updated in a while.

There are a few AWN applets from this PPA that can't be installed, so I decided to rebuild the packages in the main WebUpd8 PPA. Update: I added Ubuntu 14.04 / Linux Mint 17.x packages to the PPA.

The latest Plank 0.11.0 adds docklets support (the first four icons from the dock in the screenshot above are docklets: show desktop, clipboard manager, clock and trash), migration to GSettings for dock settings and more. 

Plank is a simple, lightweight dock written in Vala. The application, which is available by default in elementary OS, features multiple hide modes, customizable screen position, theme and icon size, supports pinning apps to the dock, quicklists and more.

Cairo Dock (Glx Dock) is a launcher / task manager that comes with a huge list of applets and configuration options.

It can be used with any desktop environment / shell, so it works with GNOME Shell, Unity, Xfce, KDE and so on. There's also a stand-alone Cairo Dock session - select "Cairo Dock" from the login menu to use it.