You may or may not be familiar with the award-winning concrete5 content management system (CMS). It is easy (or easier) to use than Wordpress and as good for development (or better) than Drupal. One of the latest features in concrete5 is multi-site content management. Basically the ability to manage multiple sites from a single installation. This works well for small businesses that need to manage multiple location websites, government agencies or for a large enterprise with a large number of high trafficked websites with individual needs.