Blogs:
WordPress
b2evolution
LifeType
Dotclear
Textpattern
Nucleus
Serendipity
Open Blog
eggBlog
Pixie
WordPress MU

Micro Blogs
StausNet

Portals/CMS:
Drupal
Geeklog
Joomla
Mambo
PHP-Nuke
Website Baker
sNews
Pligg
MODx
Typo3
Xoops
Zikula
Dolphin
Concrete5
phpwcms

Discussion Boards/Forums:
phpBB
SMF
AEF
XMB
MyBB
Phorum
PunBB
UseBB
FluxBB
bbPress

Customer Support:
Crafty Syntax Live Help
Help Center Live
osTicket
PHP Support Tickets
Support Logic Helpdesk
Support Services Manager

Discussion Boards/Forums:
phpBB
SMF

E-Commerce:
CubeCart
OS Commerce
Zen Cart
Freeway
OpenCart
PrestaShop
phpShop
Magento
WHMCS
AccountLab plus

FAQ:
FAQMasterFlex


Image Galleries:
4images Gallery
Coppermine Photo Gallery


Mailing List:
PHPlist

Polls and Surveys:
Advanced Poll
LimeSurvey
phpESP

Project Management:
PHProjekt
dotProject

Site Builders:
Templates Express

Wiki:
PhpWiki

Other Scripts:
Dew-NewPHPLinks
Moodle
Open-Realty
OpenX
PHPauction
phpFormGenerator
WebCalendar