The Domain Access project is a group of lightweight modules that provide tools for running a group of affiliated sites from one Drupal installation and a single shared database. The module allows you to share users, content, and configurations across a group of sites such as:
<-- can use any domain string
<-- treats non-standard ports as unique
By default, these sites share all tables in your Drupal installation. The Domain Prefix module allows for selective, dynamic table prefixing for advanced users.
The module uses Drupal's Node Access system to determine what content is available on each site in the network. Unlike other multi-domain modules for Drupal, the Domain Access module determines user access based on the active domain that the user is viewing, rather than which group or site the user belongs to.
Most of the documentation for Domain Access can be found in its README.txt file.