The World of Warcraft Updating System is a standalone application that automates the task of keeping your add-ons current.
Anyone that has been playing World of Warcraft for any length of time knows how frustrating a new content patch can be. The scripting system in WoW is under constant modification to help add-on writers; unfortunately this does result in add-ons breaking quite often and requires them to be updated - a very time-consuming effort if you have more than a few installed.
WoWus was created to help alleviate the pains of keeping your installation in workable order; please see the Features section on the official website for further information. WoWus also fully supports updating of addons from WoWAce.