Blogs - Wordpress
Chats - phpFreeChat
Commerce - Magento, osCommerce, Zen Cart, OpenCart, TomatoCart, CubeCart
Content Management - Drupal, Joomla, Mambo, Moodle, phpWebSite, PHP-Nuke
Forums
Mailing List - phplist, Dada Mail
Photo Gallery - Coppermine Photo Gallery, Zenphoto
Polling - Lime Survey, Advanced Poll
Project Management - PHP Guestbook, dotProject
Social Networking
Wiki
CRM - SurgarCRM, vtiger CRM
Calendar - WebCalendar
Support Tickets - PHP Support Tickets, osTicket, Support Logic Helpdesk, Help Center Live
Form Generator - PHP Form Generator
ChurchInfo Database Program
Classifieds
Realty - Open-Realty