Central Washington University CSS Referencesmain content
Might as well start at the source with W3C's Cascading Style Sheets reference. Another good resource is HTML Writers Guild's CSS FAQs.
You may also wish to check out About.com's links to CSS - Cascading Style Sheets
The Web Design Group has put together a site with beginning information on using Cascading Style Sheets. The House of Style is comprehensive resource for web developers who want to work with Cascading Style Sheets. They produce a commercial CSS editor called Style Master.
Other CSS references available online include RichInStyle.com, CSS layout techniques: for fun and profit, and Eric Meyer's CSS Work and CSS/Edge
Index DOT Css bills itself as THE Advanced CSS Resource. ZVON.org's CSS tutorials are useful as well.
css Zen Garden is almost everyone's favorite place to admire the power and beauty of CSS. The CSS Vault was created as a place to look at a list of sites that would inspire my creativity with CSS.