Virtual Domains is a Component for Joomla (>=1.5) that provides Multi Domain Support.

The idea of Virtual Domains, it is, to have two or more sites with different design and partially different content and functionality, but without the necessarity to manage consistent content multiple.

This can be achieved with Joomla in combination with Virtual Domains, by defining for each website/domain a special template and specifying what menu should be the starting point for the site.