Blogs:
WordPress
b2evolution
LifeType
Dotclear
Textpattern
Nucleus
Serendipity
OpenBlog
eggBlog
Pixie
PivotX
Chyrp

Micro Blogs:
StatusNet
PageCookery
Sharetronix
Storytlr

Portals/CMS:
Zikula
Joomla
Geeklog
Mambo
PHP-Nuke
Website Baker
sNews
Pligg
MODx
Xoops
Typo3
Concrete5
phpwcms
e107
CMS Made Simple
Contao
ocPortal
PyroCMS
Zazavi Website Builder
PHP-Fusion
Silex
Saurus
jCore
Fork
Hotaru CMS
Mahara

Forums:
Advanced Electron Forums
PhpBB
XMB
MyBB
Phorum
PunBB
Simple Machines Forum
UseBB
FluxBB
bbPress
Vanilla
FUDforum
miniBB

Wikis:
MediaWiki
DokuWiki
PhpWiki
PmWiki
TikiWiki
WikkaWiki

Music:
kPlaylist
Podcast Generator
Impleo
AmpJuke

Mail:
phpList
Webinsta Maillist
poMMo
ccMail
OpenNewsletter

Calendars:
WebCalendar
phpicalendar
phpScheduleIt
ExtCalendar

Social Networking:
Elgg
Dolphin
Jcow
Oxwall
Beatz
Etano
PeoplePods

Ad Management:
Noahs Classifieds
OpenX
Kamads
PHPads
OpenClassifieds
GPixPixel
OSClass

Video:
ClipBucket
VidiScript
videoDB

Gaming:
Shadows Rising
Word Search Puzzle
Multiplayer Checkers
BlackNova Traders

Polls and Surveys:
LimeSurvey
phpESP
EasyPoll
LittlePoll
Simple PHP Poll
CJ Dynamic Poll
Advanced Poll
Piwik

Project Management:
dotProject
phpCollab
PHProjekt
NetOffice
ProjectPier
Mantis Bug Tracker
SugarCRM
Feng Office
eyeOS
Mound
The Bug Genie
TaskFreak
Collabtive

ERP:
OrangeHRM
FrontAccounting
SimpleInvoices
Dolibarr
Vtiger
BlueERP
Tine
EGroupware

E-Commerce:
Zen Cart
Freeway
osCommerce
OpenCart
PrestaShop
phpShop
WHMCS
CubeCart
AccountLab Plus
PHP Point Of Sale
TheHostingTool
TomatoCart
Avactis
phpCOIN
Quick.Cart
Axis
AlegroCart

Guest Books:
Advanced Guestbook
phpBook
BellaBook
VX Guestbook
Lazarus
RicarGBooK
PHPKode Guestbook

Customer Support:
Crafty Syntax
Help Center Live
HESK
osTicket
ExoPHPDesk
phpSupport
Open Web Messenger
phpOnline
phpMyFAQ
iQDesk
Trellis Desk

Frameworks:
CodeIgniter
PHPDevShell
PRADO
Symfony
yii
Zend
DIY
PhpOpenBiz
xAjax
AjaxAC
Kohana
Smarty
Symfony
WideImage
HTML Purifier

Educational:
Moodle
Claroline
ATutor
TCExam
DoceboLMS
Omeka
eFront
Moodle_2.0

Database Tools:
phpMyAdmin
Adminer
SQLiteManager
Vty
MyWebSQL

Image Galleries:
Coppermine
TinyWebGallery
Gallery
LinPHA
Piwigo
Pixelpost
ZenPhoto
phpAlbum
Shutter
4images
Plogger

JS Libraries:
script.aculo.us
jQuery
Ext JS
Scripty2
MochiKit
MooTools
YUI
Prototype
Rico
Dojo
AJS
Raphael
Sizzle
PaintbrushJS
jqPlot
PHPlot
Elycharts
jsMorph
php.JS
Modernizr
JSZip

Perl:
Movable Type

RSS:
Gregarius
SimplePie
Feed on Feeds
selfoss

Others:
FAQMasterFlex
phpLD
Open-Realty
WeBid
PHPfileNavigator
cFTP
PhpGedView
phpFormGenerator
OpenDocMan
YOURLS
phpFreeChat
PHP QR Code
LetoDMS
Form Tools
phpDocumentor
Hablator
Arfooo
PHPWeby
Arfooo
PASTE
Open Journal Systems
OpenBiblio
Seo Panel
Soholaunch Website Builder
jobberBase
Question2Answer
JoobsBox
WIODE
ArticleSetup