phpBB: A widely-popular open-source bulletin-board, forum package.  Host and moderate forums.

4Images Gallery: An Image Gallery system featuring unlimited categories/subcategories, web-based and FTP images upload, auto-thumbnails, comments.

Coppermine: Recommended image Gallery system featuring categories and albums, thumbnails and intermediate size pics.  Based on the phpBB system and can be integrated into it.

b2evoltion: A blog script featuring multiple blogs, categories/sub-categories, skins, search function, multiple languages, search engines friendly URLs.

Crafty Syntax Live Help: A Live Help chat system to monitor your visitors, proactively open a chat session.  We use a version of it ourselves on our site.

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

Drupal: An advanced portal with collaborative book, search engines friendly URLs, online help, roles, full content search, site watching, threaded comments, version control, blogging, news aggregator.

FAQ MasterFlex: Unlimited categories/questions/answers, web-based administration.

GeekLog: A portal system with a wide range of modules.

Help Center Live: Very powerful all-in-one help center including Live Help, Support Tickets and FAQ.

Joomla: Oone of the most powerful Open Source Content Management Systems on the planet. It is used all over the world for everything from simple websites to complex corporate applacations.

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.

Moodle: A course management system designed to help educators create quality online courses. Available in 34 languages and features a WYSIWYG HTML editor.

Noah's Classifieds

Open Realty: A Real Estate listing system featuring attachments, flexible search, template system and Yahoo Maps.  Users have also used this to create other listing sites such as used car sites, etc.

osCommerce: A recommend open source shopping cart system.

osTicket: A Support Tickets system featuring email piping, pop3 login, unlimited email addresses, admin/staff/user panels.

php Form Generator: 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.

PHP List: A powerful mailing list which is capable of sending emails in controlled matches, allows users to opt-in and out of lists.

phpNUKE: One of the most popular community-based portals with a big choice of modules and languages.

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.

phpwiki: PhpWiki is a web site where anyone can edit the pages through an HTML form. Linking is done automatically on the server side.  Much like the popular wiki's used around the internet.

postnuke: A Content Management System with focus on flexibility and security. A big variety of modules and blocks makes this CMS an allround tool.

Siteframe: A straightforward content-management system designed for rapid deployment of community-based websites.

Tikiwiki: Used to create all sorts of web applications, sites, portals, intranets and extranets. TikiWiki also works great as a web-based collaboration tool.

TYPO3: Open Source content management system.

WebCalendar: Private and public calendars.

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.

Xoops: A very popular advanced portal system.

Zen Cart: A user-friendly, open source shopping cart system.