Tutorials
Tao HTML (The Art of HTML)
A stylish Web site devoted to composing good HTML.
Writing HTML
A series of lessons on writing HTML pages provided by the Maricopa Center for Learning and Instruction.
Introduction to HTML and Intermediate HTML
Two tutorials from Case Western Reserve University
A Beginner's Guide to HTML
A useful resource for beginners, from the National Center for Supercomputing Applications (NCSA).
How do they do that with HTML?
Tips on how to do tables & frames, access counters, animated GIFs, and other cool things.

Reference Guides
HTML Reference Manual
From the Sandia National Laboratories, documentation and background on HTML.
Site Builder Workshop: Authoring/Editing
Microsoft's guide to using HTML, with links to HTML extensions for Internet Explorer.
Creating Net Sites
HTML reference guides, tutorials from Netscape. Includes overview of Netscape extensions to HTML.
The HTML Station
A quick-reference guide to HTML tags, with examples of how they render in a browser.
The Barebones Guide to HTML
A comprehensive list of tags in the HTML 3.2 spec, in several languages.
Cross-Referenced List of HTML Tags
From the Willcam Group, a well-indexed guide to HTML 2.0 and 3.2.

Downloadable HTML Help
HTML Reference Library
Thorough documentation to the HTML standard, including proprietary Internet Explorer, Mosaic and Netscape tags, in Windows help format.
Microsoft HTML Help
Customize your Windows 95 environment to maintain HTML documents.
Microsoft HTML Wizard
HTML Wizard is a simple but useful tool that adds functionality to the Microsoft Windows 95 interface for HTML files.
Doctor HTML
A tool that checks your HTML syntax, from Imagiware, Inc.

Where to go for more
The HTML Writers Guild: HTML Resources
Yahoo! -- HTML
ZDNet Whole Web Catalog Web Kitchen