http://www.aardvarktopsitesphp.com/index.php?page=demo

Aardvark Topsites PHP is a free topsites script built on PHP and MySQL.

Coppermine is a multi-purpose fully-featured and integrated web picture gallery script written in PHP using GD or ImageMagick as image library with a MySQL backend.

http://cutephp.com/

Cute news is a powerful and easy to use news management system that uses flat files to store its database. It supports commenting, archives, search function, file upload management, backup & restore, IP banning, flood protection ...

http://expressionengine.com/

ExpressionEngine is a flexible, feature-rich content management system that empowers thousands of individuals, organizations, and companies around the world to easily manage their website.

http://fudforum.org/forum/

FUDforum is a highly customizable forum package, with a large feature set. The easy to use administration control panel allows the administrator to easily configure and control the many features available. The forum also includes an interactive help package, which helps to familiarize users with the full potential of FUDforum.

http://gallery.menalto.com/

Gallery gives you an intuitive way to blend photo management seamlessly into your own website whether you're running a small personal site or a large community site.

http://www.jaws-project.com/

Jaws is a Framework and Content Management System for building dynamic web sites. It aims to be User Friendly giving ease of use and lots of ways to customize web sites, but at the same time is Developer Friendly

http://www.joomla.org/

Joomla is an award-winning content management system (CMS), which enables you to build Web sites and powerful online applications. Many aspects, including its ease-of-use and extensibility, have made Joomla the most popular Web site software available. Best of all, Joomla is an open source solution that is freely available to everyone.

http://www.mediawiki.org/wiki/MediaWiki

MediaWiki is a free software wiki package originally written for Wikipedia. It is now used by several other projects of the non-profit Wikimedia Foundation and by many other wikis, including this website, the home of MediaWiki.

http://moodle.org/

Moodle is a course management system (CMS) - a free, Open Source software package designed using sound pedagogical principles, to help educators create effective online learning communities.

http://www.oscommerce.com/

osCommerce Online Merchant is an Open Source online shop e-commerce solution that is available for free under the GNU General Public License. It features a rich set of out-of-the-box online shopping cart functionality that allows store owners to setup, run, and maintain online stores with minimum effort and with no costs, fees, or limitations involved.

http://www.phorum.org/

Started in 1998, Phorum was the original PHP and MySQL based Open Source forum software. Phorum's developers pride themselves on creating message board software that is designed to meet different needs of different web sites while not sacrificing performance or features.

http://www.phpbb.com/

No other bulletin board software offers a greater complement of features, while maintaining efficiency and ease of use.

http://sourceforge.net/projects/php-fusion/

PHP-Fusion is a light-weight open-source content management system (CMS) written in PHP 5 (compatible with PHP 4). It utilizes a MySQL database to store your site content and includes a simple, comprehensive administration system.

http://www.php-nuke.org/

PHP-Nuke is a web based automated news publishing and content management system based on PHP and MySQL.

http://www.punbb.com

PunBB is a fast and lightweight PHP-powered discussion board. It is released under the GNU General Public License. Its primary goals are to be faster, smaller and less graphically intensive as compared to other discussion boards.

http://www.simplemachines.org/

Simple Machines Forum — SMF in short — is a free, professional grade software package that allows you to set up your own online community within minutes.

http://www.typo3.com

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

http://www.vbulletin.com

vBulletin is a professional, affordable community forum solution. Thousands of clients, including many industry leading blue chip companies, have chosen vBulletin - It's the ideal choice for any size of community.

http://www.vbulletin.com/features_blog.php

vBulletin Blog is a fully-featured blogging add-on that enables community members to create their very own online blogs within vBulletin. Giving members a place to post thoughts, ideas and musings will keep users returning to the community again and again, and advanced administration features allow forum owners and moderators to keep control and integrate Blog into vBulletin’s existing look and feel.

http://wordpress.org/

WordPress is a state-of-the-art publishing platform with a focus on aesthetics, web standards, and usability. More simply, WordPress is what you use when you want to work with your blogging software, not fight it.