Networks for WordPress a plugin by ddean addsa Networks panel allowing network admins to create and manage multiple Networks from one WordPress installation. Each Network can exist on its own domain, and have its own set of blogs / sites.
Each Network can have its own set of plugins, themes, administrators, permissions, and policies, but all will share a database of user accounts.
Sites can be moved freely among Networks.
The author says:
Each Network will require changes to your webserver and manual file changes. You can choose: changing WordPress core files once or creating new files for each Network.
How do I set up new domains to work with a single WordPress install?
Your webserver must direct requests for each domain you want to use to your WordPress files, info at: http://wordpress.org/extend/plugins/networks-for-wordpress/faq/
Download and info: http://wordpress.org/extend/plugins/networks-for-wordpress/