Moodle is a course management system that allows educators to create online learning communities for their students. It has an open design with a large developer community creating plugins, themes and modules. It's used all over the world in environments large and small and is one of the better supported Open Source course management systems. The JumpBox for Moodle is a great way to get up to speed with Moodle and requires a minimal investment in time and money.

Joomla! is arguably the world's most popular open source content management system for public facing web sites. Joomla 1.5 is a ground-up rework of the Joomla 1.0 code base moving it to a true MVC architecture.

Wordpress is the leading open source blogging platform that has rocketed to popularity thanks to its open design and powerful features.

Drupal is an open source, web content management (WCM) system. It provides a simple, intuitive interface that allows an individual or a community of users to easily publish, manage and organize a wide variety of content on a website without programming skills.

Joomla! is an award-winning Content Management System (CMS) that will help you build websites and other powerful online applications.

Alfresco is an Open Source Enterprise Content Management (ECM) system that provides features for Document Management, Collaboration, Records Management, Knowledge Management, Web Content Management and Imaging. Alfresco has the goal of providing an Open Source ECM system that surpasses commercial ECMs in terms of features, functionality and benefits to the user community.

Silverstripe is a standards-compliant content management system that allows the user to manage a dynamic content site. Silverstripe utilizes MVC architecture and has a desktop feel with its use of AJAX-based controls.