Simply a plank dock theme that doesn't look like Unity but gives you a similar interface:
After installing my theme just go to plank's preferences and set:
- Position: left
- Alignment: panel-mode
- ItemsAlignment: left
If you are using cinnamon (like me :), you can install Window Buttons with Title applet (http://cinnamon-spices.linuxmint.com/applets/view/184) and Cinnamon Maximus extension (http://cinnamon-spices.linuxmint.com/extensions/view/29) to make your interface more like Unity.
Just copy Unity-like directory to /usr/share/plank/themes/ or to ~/.local/share/plank/themes/. After that you can choose it via plank's settings.
Arch linux users can simply install my package from AUR: https://aur.archlinux.org/packages/unity-like-plank-theme/.