This plugin is used to add functionallity for WordPress MU to create a Google Sitemap XML. Please note that this will add links to all public pages, posts of all the blogs.
If you like you can modify your .htaccess file and add the following to have a nicer URL:
RewriteRule ^sitemap.xml$ ?sitemap=wpmu-gs [QSA]
Requires WordPress Version: 2.9.2 or higher