Blogs:
b2evolution: A blog script featuring multiple blogs, categories/sub-categories, skins, search function, multiple languages, search engines friendly URLs.
Visit b2Evolution

Nucleus: A powerful blog script featuring multiple blogs, multiple authors, drafts and future posts, bookmarklets.
Visit Nucleus

pMachineFree: This is a features limited version of pMachinePro. You need a license, in order to use pMachine Free on commercial or profit oriented websites
Visit pMachine

Wordpress: WordPress is a personal publishing tool with focus on aesthetics and featuring cross-blog tool, password protected posts, importing, typographical niceties, multiple authors, bookmarklets.
Visit Wordpress


Content Management Systems - Content Management Tools:
Drupal: An advanced content management system with collaborative book, search engines friendly URLs, online help, roles, full content search, site watching, threaded comments, version control, blogging, news aggregator.
Visit Drupal

Geeklog: A content management tool with a wide range of modules.
Visit Geeklog

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.
Visit Mambo

PHP-Nuke: One of the most popular community-based content management tool with a big choice of modules and languages.
Visit PHP-Nuke

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.
Visit PHP-Website

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

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

Xoops: A very popular advanced portal content management tool.
Visit Xoops

phpWCMS: phpwcms is an Open Source web content management system released under the GNU General Public License. You can use it for free. phpwcms is optimized for fast and easy setup and works on any standard webserver platform that supports PHP/MySQL and was tested successfully on Windows 2000/XP, MacOSX and LINUX. 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
Visit phpWCMS


Wiki:
PhpWiki: A WikiWikiWeb is a web site where anyone can edit the pages through an HTML form. Linking is done automatically on the server side; all pages are stored in a database.
Visit phpWiki

TikiWiki: Tiki CMS/Groupware (aka TikiWiki) is a powerful open-source Content Management System (CMS) and Groupware that can be used to create all sorts of Web applications, Sites, Portals, Intranets and Extranets. TikiWiki also works great as a Web-based collaboration tool.
Visit TikiWiki


Customer Service Software - Customer Support:
Crafty Syntax Live Help: A Live Help chat system featuring monitor your visitors, proactively open a chat session, multiple chat sessions, referer tracking, page view tracking, multiple operators, canned responses/images/URLs, multiple departments each with different icons, leave a message.
Visit Crafty Syntax

Help Center Live: Very powerful all-in-one help center including Live Help, Support Tickets and FAQ. Features include unlimited operators/departments, monitor visitors, initiate chat, collect visitor's information, track visitor's footprint, autosave chat transcripts, canned messages, leave a message, auto-assign tickets to operators, unlimited FAQ topics.
Visit Help Center Live

osTicket: A Support Tickets system featuring email piping, pop3 login, unlimited email addresses, admin/staff/user panels, avoid autoresponder loops, limit maximun tickets user can have opened, accept attachments and limit size, pager alerts for admin.
Visit osTicket

PHP Support Tickets: A simple, one-admin Support Tickets system featuring self-registering, emailing to admin, attachments.
Visit phpSupport Tickets

Support Logic Helpdesk: A Support Tickets system featuring multiple email addresses, admin/staff/user panels, canned responses, HTML tags support, email limit on a per user/day basis, attachments.
Visit Support Logic Helpdesk

Support Services Manager:
Visit Support Services Manager

Discussion Boards:
Invision Board:
Visit Invision Board

phpBB2: A widely-popular open-source bulletin-board package, works well, simple user interface and admin panel, clean look, scales well, and can be customized.
Visit phpBB2

E-Commerce:
CubeCart: An easy to use yet powerful shopping cart featuring unlimited categories and products, multiple payment gateways, downloadable products. The design is very easy to modify.
Visit CubeCart

OS Commerce: A power-user shopping cart with a big variety of modules and support of almost every payment gateway. A big developers community is ready to offer custom solutions depending on your needs.
Visit osCommerce

Image Galleries:
4Images Gallery: An Image Gallery system featuring unlimited categories/subcategories, web-based and FTP images upload, auto-thumbnails, comments, send a picture, rate a picture, random pictures, extensive administration panel.
Visit 4Images

Coppermine Photo Gallery: An Image Gallery system featuring categories and albums, thumbnails and intermediate size pics, search feature, new and random pictures, user management (private galleries, groups), user comments, e-cards feature, slideshow viewer.
Visit Coppermine

Gallery: An Image Gallery system featuring albums within albums, thumbnailing specific picture area, captions, rotate, reorder pictures, album-based attributes, album mirroring.
Visit Gallery


Mailing List:
PHPlist: A powerful mailing list featuring multiple mailing lists and attachments.
Visit PHPList

Project Management - Project Tracking:
dotProject: Project Management featuring companies, projects, tasks (with Gantt charts), forums, files, calendar, contacts, tickets/helpdesk, language support, user/module permissions, themes.
Visit Dot Project

PHProjekt: Project Management featuring optional group system, privileges, calendar, contacts, time card, projects, chat, forum, request tracker, mail client, files, notes, bookmarks, to-do list, reminder, voting, language support.
Visit PHPProjekt

FAQMasterFle: Unlimited categories/questions/answers, web-based administration.
Visit FAQMasterFlex

Moodle: A Course Management System designed to help educators create quality online courses. Available in currently 34 languages, featuring WYSIWYG HTML Editor, teacher has full control over all settings for a course, flexible array of course activities (Forums, Journals, Quizzes, Resources, Choices, Surveys, Assignments, Chats, Workshops), user logging and tracking, mail integration and much more.
Visit Moodle


Other Scripts:
Noahs Classifieds: A classifieds system featuring categories and subcategories in unlimited depth, image upload for categories and classifieds, variable fields per categories, customizable email notifications, locking categories, classifieds approval, auto-thumbnail generation, classifieds management by user, send classified to a friend.
Visit Noah's Classifieds

Open-Realty: Real Estate listing system featuring attachments, flexible search, template system, Yahoo Maps interface.
Visit Open Realty

phpAdsNew: A highly professional complete ad server featuring different types of ads, display based on keywords, zones, hour of the day, day of the week, extensive statistics, client statistics.
Visit phpAds

PHPauction: The GPL version of PHPauction featuring email notification of bids, attachments, reserve price, minimum bids, standard and dutch auctions, bid history, send auction to a friend, highest bids, auctions ending soon.
Visit phpAuction

phpFormGenerator: A form generator featuring up to 100 form fields, all kind of input fields incl. file upload, customizable fields attributes, send submitted data to an email address or store them in a database, admin panel.
Visit phpForm Generator

WebCalendar: A very powerful webcalendar featuring private and public calendars.
Visit WebCalendar

phpCOIN: A full billing/invoicing application, perfect for webhosting resellers.
Visit phpCoin

Polls and Survey systems:
Advanced Poll: Polling system with powerful administration tool. It features: multiple polls, templates, unlimited options, multi-language support, IP-Logging, IP-Locking, cookie support, comment feature, vote expire feature, random poll support and more. Supports textfile and mySQL database.
Visit Advanced Poll

PHPSurveyor: Develop, publish and collect responses to surveys. Display surveys as single questions, group by group or all in one page or use a dataentry system for administration of paper-based versions of the survey. PHP Surveyor can produce 'branching' surveys (set conditions on whether individual questions will display), can vary the look and feel of your survey through a templating system, and can provide basic statistical analysis of your survey results.
Visit PHPSurveyor

phpESP: PHP scripts to let non-technical users create surveys, administer surveys, gather results, view statistics. All managed online after database initialization. MySQL database backend.
Visit phpESP