Open Source CMS

I have been looking for an Open Source Content Management System (CMS) to replace WordPress. WordPress is great for blogging and it can be used as a CMS, but I really wanted something a little more robust. Here are a few of the ones I have found:

Drupal An advanced portal with collaborative book, search engines friendly URLs, online help, roles, full content search, site watching, threaded comments, version control, blogging, news aggregator.

Geeklog A portal system with a wide range of modules.

Joomla Joomla! is one of the most powerful Open Source Content Management Systems on the planet. It is used all over the world for everything from simple websites to complex corporate applications. Joomla! is easy to install, simple to manage, and reliable.

Mambo Open Source A professional level yet easy to use Content Management System featuring inline WYSIWYG content editors, newsfeeds, syndicated news, banners, mailing users, links manager, statistics, content archiving, date based content, 20 languages, modules and components.

PHP-Nuke One of the most popular community-based portals with a big choice of modules and languages.

phpWCMS phpWCMS is perfect for professional, public and private users. It is very easy to learn and gives you the flexibility to separate layout and content. Lots of powerful but simple implemented features assists publishers and web developers too.

phpWebSite Very powerful Content Management System with document manager, announcements, menu manager, photo album, block maker, FAQ, web pages maker, polls, information categorizer, calendar, link manager, form generator.

Post-Nuke A Content Management System with focus on flexibility and security. A big variety of modules and blocks makes this CMS an allround tool.

Siteframe A straightforward content-management system designed for rapid deployment of community-based websites. Nice-looking templates, oriented toward document-sharing, clean interface.

TYPO3 TYPO3 is a free Open Source content management system for enterprise purposes on the web and in intranets. It offers full flexibility and extendability while featuring an accomplished set of ready-made interfaces, functions and modules.

Xoops A very popular advanced portal system.

Also EasyCMS
MySource Matrix
WebGUI
Plone

Also found a good reference for all Open Source Content Management Systems.