Here are some cool tools for LAMP developers

GUI Development Framework:

http://developer.yahoo.com/yui/
http://www.prototypejs.org/
http://dojotoolkit.org/
http://mootools.net/
www.jquery.com (Java script library)

Unit Testing Tools:
http://phpunit.sourceforge.net/
http://code.google.com/p/snaptest/ (Recommended by Jason)
Simple Test (Not recommended)

QA Automation Tools:
Selenium - QA Automation Tool

Search Engine:
Lucene

Project Management Tools:
Projectpath (Can anyone provide the URLs??)
Project Wiki (Anyone can provide the links??)

Systems Monitoring Tool:
http://www.nagios.com

Note: Any other attendee, if you remember anything else, please add the comments.