Optimisation

Smartsaver Pro
JPEG Optimiser
Cyberview ImagePro

Validation

www.htmlhelp.com/tools/validator
www.htmlhelp.com/tools/csscheck
WC3 Validator

Dynamic HTML

BrainJar
DHTML Guru Resource
Dynamic Drive DHTML Code Library
Dynamic HTML Lab
Bratta.com

Free Site Search Engines

Freefind.com
Atomz.com

Active Server Pages

W3 Schools
LearnASP.com
DevASP.com

PHP

php.net
zend.com

Search engines promotion

Search engine watch
(Everything you need to know about search engine submissions!)

The following sites will submit your site to multiple search engines FOR FREE!
Jimtools.com
Addme.com
Ineedhits.com
Dreamsubmit.net
Web Site Search Engine Optimization Strategies
Offers SEO techniques. Covers search engine optimization process, including keyword research, on-page and off-page ranking tips, unethical search engine optimization techniques.

Search engine add URL pages

AltaVista
Fast (AllTheWeb)
Hotbot/Lycos
Lycos
Northern Light
UKMax
Webcrawler
Infoseek/Go
Inktomi
Go
Google
Excite/Magellan
Excite UK
Canada
DirectHit
AskJeeves

Cascading Style Sheets

A List Apart
Glish.com
Web Standards.Org
Devshed
W3Consortium CSS guides
Zeldman.com
Webreference.com
Western Civilization
htmlhelp.com
Web Site Abstraction

Free Javascripts

Smartscript
Website Abstraction
Web Teacher
Javascripts.com
Scripts.co.uk
Developer.com
ZDNet Developer script library
Factorymarket.com
Plexus.com
CGI Script
Internet.com
Gatescript.com
Javascriptkit.com

Help with Keywords

Overture
Northernwebs
Scrub the web