While I've taught introductory HTML a few times, I did little more than scratch the surface of HTML and barely even discussed such related areas as scripting technologies, cascading style sheets, cross-browser issues, much less really juicy stuff like Ajax. The following resources will help you find out as much more as you really feel you want to know. I expect that I'll be adding to the list as other ideas for inclusion occur to me, or if you ask for additional categories. And, you can ask by contacting me.

The Specifications

W3C Technical Reports and Publications:
The World Wide Web Consortium (W3C) creates and maintains the specifications for HTML and related technologies. This is the official source for the currently approved recommendations. Note: Just because it has been approved, it does not follow that it has been implemented.

Inspiration

Salem @ nationalgeographic.com:
This is an old one, but itwas the first site to convince me that frames are not necessarily evil. It was a site I wish that I had built.

Anti-Inspiration

B U D . U G L L Y . D E S I G N:
Does looking at elegantly crafted sites get you down? Tempted to give up because the bar just looks as though it's set too high? Visit this site. Ghastly color combinations, annoying animated graphics, eregious misspellings, error-laden scripts, broken code, every mistake you could possibly think of, and some that would never occur to you, may be found here.

Validators and Emulators

W3C HTML Validation Service:
Run by the folks who create the specifications: who better to check out your work?

Watchfire WebXACT:
This online validator focusses specifically on those elements of a web page that can cause problems for the disabled, especially those using speech-based browsers. If you're designing for a general audience, it's worth checking your pages through this validator.

HTML Editors

Wait! Am I saying that you don't need to learn HTML after all? Well, it depends, dear: how good do you want your pages to be? Do you want to be able to exert as much control over their presentation as HTML will allow? Do you want your pages to work across different platforms and browsers? Do you want to minimize download times? Then yes, you needed to learn HTML. Use of a good editor, however, can streamline some of your work.

Dreamweaver:
The only non-freebie on this list, Dreamweaver has long been the darling of the dedicated web geek community. It comes with an HTML editor bundled in and is noted for (among other things) leaving your own code alone.

Usability

Alertbox: Jakob Nielsen's Column on Web Usability:
Nielsen is considered the usability guru (even by those who decry his conservative approach to design). His bi-weekly column addresses such issues as user testing, fighting linkrot, how people read on the web, and effective design.

Art and the Zen of Web Sites:
I found this (long) essay on web design very early on in my webgeekstress career and took it much to heart. Some of my favorite quotes include:

"People don't go to the FedEx web site to be entertained any more than they go to a FedEx office to be entertained."
"If you really believe that it's okay to change the meaning of interface elements, then it's a good thing you're designing web pages and not airplane cockpits."

The Looks of the Thing

safe colors:
The web safe color palette. It's probably no longer necessary to restrict yourself to the so-called web safe palette. However, it's values are frequently the available defaults in HTML and image editing software, so it's handy to have as a reference.

Tutorials and Tips

A List Apart:
"A List Apart Magazine (ISSN: 1534-0295) explores the design, development, and meaning of web content, with a special focus on web standards and best practices." Usually one of the first places I go when I have a new problem.