Spartan UI
http://wow.curse.com/downloads/wow-addons/details/spartan-ui/download/245188.aspx
I really like this addon, one of my favorites.
Taken from Curse.com:
SpartanUI is designed to free your screen by moving a majority of the interface elements to the bottom. It is the new look for World of Warcraft. Created by Ansu of Dalaran (aka Atriace) and maintained by Beladona. This is an original design developed through painstaking effort and the help of users and fans at spartanui.com;