This tutorial will guide you through setting up WPMU on a shared host like godaddy.com. After you set this up properly, you will be able to run unlimited websites on your host, each with a different domain name and website theme. This will save you money because you can use the cheapest hosting, which usually does not allow for parking domains into separate folders. It also allows you to create a large community just like wordpress.com where you control all the plugins and themes.