Make a portal or simple blog using these free open source CMS downloads.

Joomla

Joomla is a is a rebranded release of Mambo. It’s very easy to use and can be used by a person that doesn’t know anything about coding. Almost anything is configurable or editable through the included admin panel and there are tons of third party modules and templates available for it.

Pros: Large community of users .
Cons: Sometimes difficult to locate a feature or setting. Slow load time.

Drupal

The software from the now defunct drop.com evolved into Drupal. Drupal can be morphed into almost anything you want it to be. For example, there is a way to make Drupal into a site like Digg.com. It’s normally used for community driven web sites such as schools, projects, or company intranets.

Pros: Large community of users. Flexibility.
Cons: Takes a while to learn. Not as secure as other CMS’s.

Pligg

Pligg evolved from code from the site mename. It allows you to make a site similar to Digg where users can rate web pages. However, Pligg can be used for almost any type of article web site. Customizing the templates and getting your site customized has proven to be a chore for many of its users though.

Pros: Very flexible. Simple to edit and learn.
Cons: Low on features. Hard to find templates or modules.

Wordpress

Probably the most commonly used CMS software on the web. Wordpress is usually used for a simple blog but there are many plug-ins or modules available for it to provide more usability. Novices will find Wordpress easy to use for any simple web blogging needs.

Pros: Simple interface. Super-large community. Templates and modules are widely available
Cons: Lacks the features other CMS systems have. Constantly requires fixes for common bugs.

PHPnuke

Lots of features and modules are available for PHPnuke. It’s very simple to start a full featured portal with. Massive amounts of modules and themes are available for it. You will have to know or learn how to hack code if you want to deal with PHPnuke deeply though.

Pros: Can integrate with almost anything written in PHP. Large community of users.
Cons: Buggy. Not very secure.

Mediawiki

The CMS software used by the popular Wikipedia site. Mediawiki allows you to make a wiki site where users can edit and submit content freely. Companies have used MediaWiki for their internal knowledgebases. It’s ideal for a large scale site and handling large amounds of data efficiently.

Pros: Performance is very fast even with large amounts of data.
Cons: User accounts are hard to manage. Not very secure.

Typo3

Industrial strength CMS software for the serious CMS web builder. Typo3 (not to be confused with Typo) lets you customize almost any detail of your web site through the use of it’s advanced administrator console and the use of TypoScript. With about 2000 extensions available for it, Typo3 can do almost anything.

Pros: Many features configurable through admin interface.
Cons: Very complex to configure certain features.

Xoops

Pronounced “Zoops”, Xoops is a portal system that comes default with news, downloads and forum modules. It’s useful for sites where you have many users editing things as user permisions are detailed. It is also widely adopted as the CMS of choice by web developers who develop sites for their clients.

Pros: Easy for beginners to install and use.
Cons: Community lacks support. Buggy.

Other notable CMS software.

Simple blogging CMS

Forked from PHP-Nuke.

Light CMS for blogs.

For even more information on CMS software, there is more information here. http://opensourcecms.com/