Beginner's Guide to HTML.  A very popular guide for NCSA.

Barebones HTML.  A very nice tutorial from Kevin Werbach.

The Official HTML Specification.  This is the official HTML specification from the World Wide Web Consortium..

Sandia's HTML Reference.  A very complete HTML syntax guide from Sandia National Labs (it's quite long because all the syntax is on one page).

Top 10 Web Design Tips.  All kinds of design tips and tutorials from Dmitry Kirsanov.

D.J. Quad's Ultimate HTML Site.  Another extensive set of HTML references from Quadzilla.

Web Diner.

Creating Killer Web Sites by David Siegel.  Web site design from a designers point of view.

Splitinfinitys Top 100 web developers resources.  A nice site with HTML, CGI and many other web related resources.