An open-source blog publishing system that can be used as a content management system. It has widgets that can be moved without editing any PHP or HTML code as well as a variety of themes to choose.

Cost: Free

A blog-publishing system that can also be used as a content management system.

Cost: Free

A powerful open-source web application framework written in Python.

Cost: Free

An open-source content management system written in PHP that uses a MySQL database.

Cost: Free

An open-source modular framework and content management system with an extensive community behind it.

Cost: Free

Often used by international news media companies, SourceFabric is a multi-lingual, open-source web publishing system that can bring your newspaper or magazine content to the online world.

Cost: Free

Though these systems are free, you might need to upgrade your hosting plan in order to accommodate them. Check with your hosting provider to be sure. To compare these and other Content Management Systems, check out CMS Matrix.