The css-discuss Wiki
http://css-discuss.incutio.com
CSS Pointers Group
http://css.nu/
Web Design Group Guide to CSS
http://www.htmlhelp.com/reference/css/
RichInStyle
http://richinstyle.com
Index DOT CSS
http://www.blooberry.com/indexdot/css/
CSS Edge
http://www.meyerweb.com/eric/css/edge/
WebArchitects CSS page
http://www.webarchitects.co.uk/css/
CSS1 and CSS2 Browser Support
http://www.westciv.com/style_master/academy/browser_support/
HotSource Cascading Style Sheets guide
http://www.sbrady.com/hotsource/css/
Evil Test Suite
http://www.hixie.ch/tests/evil/mixed/
Practical CSS Layout
http://www.alistapart.com/stories/practicalcss/
From Web Hacks to Web Standards: A Designer's Journey
http://www.alistapart.com/stories/journey/
An open letter to the web design community: Why should I redesign my site with Cascading Style Sheets?
http://www.actsofvolition.com/index.cfm?section=board&id=521
Layout-o-matic
http://www.inknoise.com/experimental/layoutomatic.php
Tables or CSS: Choosing a layout
http://evolt.org/article/Tables_or_CSS_Choosing_a_layout/25/21429/index.html
The Layout Reservoir
http://www.bluerobot.com/web/layouts/
CSS Layout Techniques
http://www.glish.com/css/
Little Boxes
http://www.thenoodleincident.com/tutorials/box_lesson/boxes.html