There seem to be a million and one open source content management systems these days. Just look at Open Source CMS. The problem is none of the developers seem to actually grasp in depth search engine optimization issues that such systems create.
To help fend off the confusion, we’ve put together a list of what we feel are some of the most SEO friendly open source content management systems on the market today.

MODx allows us complete control over our templates, markup, URLs, and allows us to create template variables to our hearts desire, it is perfect for creating optimized websites.
MODX allows you to control 100% of what is output with virtually no effort. Unlike other systems that require learning complex theming engines, in MODX you work with HTML and as many custom variables for the site you need. It takes minutes to build a site that performs amazingly well in Search Engines and because site builders are in total control and can change the output at any time, making tweaks is just a few clicks away.

Concrete5 is a relative newcomer to the CMS space but has become increasingly popular based on it’s ease of use and functionality. Concrete5 sites perform quite well in the search engines and pages can be edited to include all of the necessary metadata by default. Couple this with nice clean URLs and caching and you’ve got yourself a good setup for a successful site.

There is an incredible number of plugins that can be used to extend WordPress with regards to SEO. It’s only fourth on the list because the other systems above it include these functions natively and do not require plugins. With the right selection of plugins and proper permalinks selected, WordPress is a true powerhouse when it comes to SEO.

In previous versions of Joomla (1.5 and lower) I would have excluded them completely but since 1.6 has come out, they have turned things around and introduced a ton of SEO improvements. Search engine friendly URLs, custom meta data per page (section, article, etc) have made Joomla a force to be reckoned with. It also goes without saying that it must perform well otherwise their main site wouldn’t have a page rank of 10/10 would it?

Drupal, like WordPress, relies heavily on plugins (known as modules in this instance) to enable SEO functionality at its fullest. Drupal sites typically perform quite well by default but with the addition of the right modules, it too becomes a powerhouse.