CSS

Cascading Style Sheets: Celebrating 10 Years with Style
W3C mini-site to mark the 10-year anniversary of the first published CSS recommendation. Includes time-line, hall of fame, essays, and a gallery.
http://www.w3.org/Style/CSS10/

Code Style - CSS Style Guide
Includes a cross-platform font sampler, information on media stylesheets, FAQ, and a glossary.
http://www.codestyle.org/css/

CSS Naked Day
On April 5th, simply remove all CSS from your website, stripping it entirely of its design. Promoting web standards, plain and simple.
http://naked.dustindiaz.com/

css-discuss Mailing List
Practical discussions of CSS and its use. High volume list.
http://www.css-discuss.org/

CSS3.info
Newest developments in CSS based webdesign.
http://www.css3.info/

Dive into Mark: CSS
Archive of postings to Mark Pilgrim's weblog.
http://diveintomark.org/archives/rooms/css

Eric Meyer - CSS
Articles, tutorials, discussion and resources for CSS.
http://meyerweb.com/eric/css/

EServer TC Library: Cascading Style Sheets
A collection of dozens of rated, reviewed online resources for developers who work with cascading style sheets in web and information design.
http://tc.eserver.org/dir/CSS

Web Developer's Virtual Library - Cascading Style Sheets
Teaches how to use CSS to improve the look and structure of HTML pages. Links discuss how to use CSS to avoid table layouts, colors, fonts, and layers.
http://www.wdvl.com/Authoring/Style/Sheets/

WebmasterWorld: CSS Forum
Discussions on layout, compatibility and trouble shooting.
http://www.webmasterworld.com/forum83/

W3C CSS Working Group Blog
News, announcements, and opportunities for discussion from the group working on the next CSS specification. [Atom]
http://www.w3.org/blog/CSS?tempskin=_atom