WordPress Automatic Upgrade (WPAU) is a plugin that automatically upgrades your wordpress version to the latest WordPress Version provided by wordpress.org. The plugin is designed and maintained by Keith Dsouza of Tech Buzz. For your knowledge WPAU won a WordPress Plugin Competition in the Past year organised by Weblog Tools Collection.
Most recent version of the Plugin can be found here : WordPress Automatic Upgrade Plugin
In addition to WordPress Core Upgrade WPAU also provides update solution of other plugins installed. I believe you have noticed the update notifcation feature available in the newer WordPress versions which is in my sense very helpful to be updated. Specially when you have multiple plugins installed in your wordpress system and keep a track of version update of plugins is tidious job. The New WPAU will let you install the Plugin Update automatically.