PHP - Server Side Scripting:

• PHP Manual ... very user friendly reference

HTML References:

• W3C HTML Specification ... you should be able to download a reference from here (somewhere)
• The Idocs Guide to HTML ... pretty good reference and tutorials

MySQL - open source and free database:

• MySQL Manual ... but worth getting a good SQL language refernce as well

Javascript - Client Side Scripting:

• Javascript reference ... the definitive netscape reference, may not have some IE specific features

Apache - the web server:

• Apache Home ... the main site for all things Apache, the web server used by almost all sites that know what they're doing

Chess sites:

• FIDE Handbook ... includes links to their official rules
• Chess Variant Graphics ... where I got some of the pieces from

Friends of chessish:

• Arseweb - Arsenal fan site ... run by Rupert Ward, a founder member and contributor