Web Design for Designers
Superb resource, great fonts.

Web Style Guide
Lynch & Horton, Yale. Succinct and precise.

Jakob Neilsen's Usability Site
Form following function, period.

Typical "Killer" Web Sites
Part of the CKWS site

Evolt - Faster Downloads

W3.org - the entire HTML specification.

HTML Help at the Web Design Group

W3.org's Intro to CSS

CSS Layouts and Techniques (glish.com)

css/edge
Eric Meyer's design site, including clever Javascript-free solutions for two common page features:

   Pure CSS Popups

   Pure CSS Menus

Pete Easton's color names table