Wow! This plugin steps you through the entire process of upgrading your Wordpress installs -- from checking and backing up the database to downloading the latest version from Wordpress to putting everything back together. It made my day a whole lot simpler than I ever thought it could be.
Wordpress Automatic Upgrade plugin
Wordpress Automatic Upgrade is a plugin that automatically upgrades your wordpress version to the latest files provided by wordpress.org using the 5 steps provided in the wordpress upgrade instructions.
WPAU as I call it helps you easily upgrading you to easily upgrade your wordpress installation to the latest version provided by wordpress, without having to download or upload any files.
In addition to this it automatically backups your current file and database and provides you with a link to download those. De-activates your plugins and remembers them so that after upgrading files it will re-activate those without you having to make any notes for which plugins you de-activated and the biggest saves you headaches of upgrading your wordpress installation.