Blog:
WordPress http://www.wordpress.org/
WordPress is a state-of-the-art publishing platform with a focus on aesthetics, web standards, and usability.
b2evolution http://www.b2evolution.net/
b2evolution is an advanced weblog tool, i-e software allowing you to run your own blogs, newsfeeds or even photo stream.
Life Type http://lifetype.net/
LifeType supports multiple blogs and users, media management, generation of standard content, clean URLs and support for subdomains.
Dotclear http://dotclear.org/
Dotclear is an open-source web publishing software created in 2002 by Olivier Meunier.
Textpattern http://textpattern.com/
Textpattern is a web application designed to help overcome the hurdles to publishing online, and to simplify the production of well-structured, standards-compliant web pages.
Serendipity http://www.s9y.org/
Serendipity is a PHP-powered weblog application which gives the user an easy way to maintain an online diary, weblog or even a complete homepage.
Open Blog http://www.open-blog.info/
Open Blog is a free and open source blogging platform built using the CodeIgniter PHP framework.
eggBlog http://eggblog.net/
eggBlog is the free php & mysql blog software package, allowing you to create your own online website, journal or weblog (blog) using your own web-space.
WordPress MU http://mu.wordpress.org/
Ever dream of running hundreds of thousands of blogs with a single install of WordPress? WordPress MU, or multi-user, is designed to do exactly that.
Micro Blog:
StatusNet http://status.net/
StatusNet is the open source microblogging platform that helps you share and connect in real-time within your own domain.
Portal/CMS:
Zikula http://www.zikula.org/
Zikula is a Web Application Toolkit, which allows you to run impressive websites and build powerful online applications.
Joomla http://www.joomla.org/
Joomla is an award-winning content management system (CMS), which enables you to build Web sites and powerful online applications.
Drupal http://www.drupal.org/
Drupal is an open-source platform and content management system for building dynamic web sites offering a broad range of features and services.
Mambo http://forum.mambo-foundation.org/
Mambo is a full-featured, award-winning content management system that can be used for everything from simple websites to complex corporate applications.
PHP-Nuke http://www.phpnuke.org/
PHP-Nuke is a web-based automated news publishing and content management system based on PHP and MySQL.
Website Baker http://www.websitebaker2.org
Website Baker is a PHP-based Content Management System (CMS) designed with one goal in mind: to enable its users to produce websites with ease.
sNews http://snewscms.com/
sNews is a completely free, standards compliant, PHP and MySQL driven Content Management System.
Pligg http://www.pligg.com/
Pligg is an open source Content Management System. Pligg CMS provides social networking software that encourages visitors to register on your website so that they can submit content and connect with other users.
MODx http://modxcms.com/
MODx helps you take control of your online content. An Open Source PHP application framework, it frees you to build sites exactly how you want and make them 100% yours.
Xoops http://www.xoops.org/
Xoops is an easy to use dynamic web content management system written in PHP.
Typo3 http://typo3.com/
TYPO3 is a free Open Source content management system for enterprise purposes on the web and in intranets.
Concrete5 http://www.concrete5.org/
Concrete5 makes running a website easy. Go to any page in your site, and a editing toolbar gives you all the controls you need to update your website.
Phpwcms http://www.phpwcms.de/
phpwcms is a robust and simple but yet powerful web based content management system running under PHP and MySQL.
e107 http://www.concrete5.org/
e107 is a content management system written in PHP and using the popular open source MySQL database system for content storage.
Forums:
Advanced Electron Forum http://www.anelectron.com/
AEF - Advanced Electron Forum is a free bulletin board software written in PHP and MySQL.
phpBB http://www.phpbb.com/
phpBB is used by millions of people on a daily basis, making it the most widely used opensource bulletin board system in the world.
XMB http://www.xmbforum.com/
XMB is a lightweight PHP forum software with all the features you need to support a growing community.
PunBB http://punbb.informer.com/
PunBB is a fast and lightweight PHP-powered discussion board. Its primary goals are to be faster, smaller and less graphically intensive as compared to other discussion boards.
Simple Machines Forum http://www.simplemachines.org/
SMF in short is a free, professional grade software package that allows you to set up your own online community within minutes.
FluxBB http://www.fluxbb.org/
FluxBB is a free open source forum application designed to be fast, light and user friendly.
bbPress http://bbpress.org/
bbPress is forum software with a twist from the creators of WordPress.
Image Galleries:
Coppermine http://www.coppermine-gallery.net/
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.
Piwigo http://piwigo.org/
Piwigo is a photo gallery software for the web, built by an active community of users and developers.
ZenPhoto http://www.zenphoto.org/
Zenphoto is an answer to lots of calls for an online gallery solution that just makes sense.
phpAlbum http://www.phpalbum.net/
phpAlbum is an Open Source PHP script which allows you to create your personal Photo Album / Gallery in just a seconds.
Wikis:
MediaWiki http://www.mediawiki.org/
MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
DokuWiki http://www.dokuwiki.org/
DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind.
PmWiki http://pmwiki.org/
PmWiki is a wiki-based system for collaborative creation and maintenance of websites.
TikiWiki http://www.tikiwiki.org/
TikiWiki is a CMS/Groupware which offers a large number of features "out-of-the-box" arguably more than any other Open Source Web Application.
Wikkawiki http://wikkawiki.org/
Wikkawiki is a flexible, standards-compliant and lightweight wiki engine written in PHP
Social Networking:
Elgg http://www.elgg.org/
Elgg empowers individuals, groups and institutions to create their own fully-featured social environment.
Ad Management:
OpenX http://www.openx.org/
OpenX provides the products and services to grow your business through online advertising.
Kamads http://kamads.com/
Kamads Classifieds Comes with easy setup and even easier to use features.
OpenClassifieds http://kamads.com/
OpenClassifieds is a free open source script for classifieds, advertisement or listings.
Calendars:
phpicalendar http://phpicalendar.net/forums/
phpicalendar is an open source php application to parse and display shared icalendar-compatible calendars on a website.
Gaming:
Multiplayer Checkers http://www.alilg.com/
Multiplayer Checkers lets your visitors challenge each other, play checkers and chat with this AJAX-enabled script.
BlackNova Traders http://blacknova.net/
BlackNova Traders is a web-based, multi-player space exploration game inspired by the popular BBS game of TradeWars.
Mails:
WEBinsta Maillist http://www.webinsta.com/mailing.php
WEBinsta maillist manager is built to provide a centralized mailing list / newsletter system for small to medium website .
CcMail http://www.cicoandcico.com/
CcMail is a free, open, powerful Mailing List Manager that doesnt require any programming knowledge.
Polls and Surveys:
LimeSurvey http://www.limesurvey.org/
LimeSurvey (formerly PHPSurveyor) is an open source online survey application written in PHP based on a MySQL.
phpESP http://phpesp.sourceforge.net/
phpESP is a script to let non-technical users create surveys, administer surveys, gather results, view statistics.
CJ Dynamic Poll http://www.cj-design.com/
CJ Dynamic Poll does exactly what it says in the title - it is a poll that changes dynamically.
Project Management:
dotProject http://www.dotproject.net/
dotProject is a web-based project management application, designed to provide project layout and control functions.
phpCollab http://www.php-collab.com/
phpCollab is an open source internet-enabled system for use in projects that require collaboration over the internet.
PHProjekt http://www.phprojekt.com/
PHProjekt is a modular application for the coordination of group activities and to share informations and document via the web.
ProjectPier http://www.projectpier.org/
ProjectPier is a Free, Open-Source, self-hosted PHP application for managing tasks, projects and teams through an intuitive web interface.
MantisBT http://www.mantisbt.org/
MantisBT is a free popular web-based bugtracking system. It is written in the PHP scripting language and works with MySQL, MS SQL, and PostgreSQL databases and a webserver.
Sugar CRM http://www.sugarcrm.com/
Sugar CRM is the world's leading provider of commercial open source customer relationship management (CRM) software.
Feng Office http://www.fengoffice.org/
Feng Office is a Collaboration Platform that enables you to manage your projects and business services.
E-Commerce:
Zen Cart http://www.zen-cart.com/
Zen Cart truly is the art of e-commerce; free, user-friendly, open source shopping cart software.
osCommerce http://www.oscommerce.com/
osCommerce is an online shop e-commerce solution that offers a wide range of out-of-the-box features.
PrestaShop http://www.prestashop.com/
PrestaShop e-Commerce Solution was built to take advantage of essential Web 2.0 innovations such as dynamic AJAX-powered features and next-generation ergonomy.
phpShop http://www.phpshop.org/
phpShop is a PHP-powered shopping cart application. It is released under the GNU General Public License.
WHMCS http://www.whmcs.com/
WHMCS is an all-in-one client management, billing and support solution for online businesses.
CubeCart http://www.cubecart.com/
CubeCart is an "out of the box" ecommerce shopping cart software solution which has been written to run on servers that have PHP & MySQL support.
AccountLab Plus http://www.netenberg.com/
AccountLab Plus supports over 180 TLDs, unlimited hosting plans, customers and servers.
Guest Books:
Lazarus http://carbonize.co.uk/Lazarus/
Lazarus is a free guestbook script written in PHP that uses your MySQL database for storage and is based upon the excellent Advanced Guestbook script from Proxy2.
Customer Support:
Crafty Syntax http://www.craftysyntax.com/
Crafty Syntax Live Help (CSLH) is an open source live support solution that helps customer support with live help functionality that can be proactively pushed to visitors to your site or requested by the consumer.
Open Web Messenger http://openwebim.org/
Open Web Messenger is an open-source live support application written in PHP and MySQL.
iQDesk http://www.iqdesk.co.uk/
iQDesk is a unique software specifically designed for freelancers, small and any type of one-person-business.
PHP Support Tickets http://www.phpsupporttickets.com/
PHP Support Tickets is a powerful, all-in-one email helpdesk / ticketing software that is incredibly easy to use.
Still more: 19 other softwares and 13 JS libraries.