General

• LinuxGuruz.com
  
• O'Reilly Open Books
  
• APress Free Books
  
• hotscripts.com
  

• HTML Tutorials
  

• Online PHP book at hudzilla.org
  
• Links from PHP Australia website
  
• PHP Tutorials
  
• Wikibooks: Programming PHP
  

• SQL Tutorials (probably for MS SQL, though)
  
• Wikibooks: MySQL
  

• How to Build a Successful Website
  
• WebTeacher
  
• Wikibooks: HTML Programming
  
• Wikibooks: CSS Programming
  
• Wikibooks: XML: Managing Data Exchange/CSS
  
• Wikibooks: Web Design/Basic HTML and CSS
  
• Yale WWW Style Manual
  
• Web Design References by University of Minnesota Duluth
  

• A-Prompt Project at the University of Toronto