A List Apart
This online magazine provides an interesting counterpoint to Nielsen, as it's philosophy balances design with usability.
Web Standards Project (WaSP)
A great place to learn why things like XHTML, CSS & ECMAScript are important, and a jumping-off point to find out more about them.
Web Style Guide
"The Book" when it comes to creating tasteful, attractive and functional websites. Together with useit.com and WaSP, this site provides an explanation for why this site doesn't sing, dance and jump around the way some sites do.
CSS Zen Garden: The Beauty in CSS Design
Ideally web sites should not use tables for page layout. (If you want to know why, check out the link to this Web Standards Project FAQ.) However many in the design community feel that pages that use CSS for layout are boring and look too much alike. This mind blowing gallery of CSS tableless websites done by graphic artists puts the lie to that notion.
Ruthsarian Layouts
Here is a collection of free CSS layouts.
Webmonkey
A great resource for tutorials and information for site designers.
HTML-Kit
A great, freeware HTML editing program. It has built-in validators and is very configurable.
FreeGraphics
A portal linking to sites offering free clip art and other graphics for the web. Many of the sites they link to require free registration.
Microsoft Typography
This is the best resource I've found for the official word on what fonts are installed with different operating systems and other software. Of particular interest is the section on Fonts and Products.
What's the right typeface for text?
Before & After magazine's guide to choosing the right typeface.
SEOmoz's Beginner's Guide to SEO
SEO stands for Search Engine Optimization. There is some really valuable information here to help you get a site listed higher. Like budgeting or getting fit, it's not complicated, but it's not easy.
W3C
The horse's mouth for everything from HTML to XML & CSS. A great place to find not only the final word, but tutorials, validation software (to test your code for compliance with the standard), and other freebies. Poke around.
IANA's Official List of Country Codes
The place to find out what .tv and .cc (and many more) stand for.
Visibone
A wonderful resource for HTML cheatsheets, color charts, and useful information.
CSS Cheat Sheet
Visibone's free online resources don't offer much for CSS, but this site does.
ASCII Codes
A Table of ASCII codes, ready for copy-and-paste use in your webpages.
W3Schools
Free tutorials, references, quizzes and examples for many different web technologies.
Dynamic Drive
Loads of code (DHTML, Javascript, and more) to copy & paste into your webpages.