Regular Websites
CSS Tutorial from SitePoint.com; offers a walk-thru; from the very beginning and as though you know absolutely nothing about Cascading Style Sheets. - CSS Beginner's Guide
http://www.sitepoint.com/article/html-css-beginners-guide
HTML Dog's CSS Tutorial for Beginners; complete with the bare essentials - just enough to get started with CSS. - HTML Dog: CSS for Beginners
http://www.htmldog.com/guides/cssbeginner/
MaxDesign is dedicated to standards-based web design; providing comprehensive CSS tutorials for the beginner, novice, and expert. - MaxDesign
http://css.maxdesign.com.au/
PMOB is dedicated showcasing examples of CSS; with tutorials and fixes for many browser bugs and known issues. - PMOB: CSS Examples
http://pmob.co.uk/
w3.org offers CSS tutorials, specifications, etc. - w3.org: CSS
http://www.w3.org/Style/CSS/