If you’re white labeling WordPress as your own CMS or simply want to add your own text and links to the WordPress dashboard footer area, this is a simple customization that you can do in under a minute. Simply paste this into your functions.php file:
function remove_footer_admin () { echo "Your own text"; } add_filter('admin_footer_text', 'remove_footer_admin');
Add in text, links, or brand it with your own logo at the bottom.
Source: WPRecipes.com
That snippet does not work for WordPress 3.0
Sorry, it works, my mistake!! :)