2011:
Learn CSS Layout
http://learnlayout.com/ -- a series of short examples on how to use CSS for layout

2010:
YouTubes by Lisa from 2CreateAWebSite
(Note from Lisa Friedrichsen -- I do not know the "Lisa" who created these YouTubes. But I love her stuff! And what a great name! Ha! At any rate, I think she has a way of teaching that is really clear. She presents her very first css lesson from a layout perspective (in my travels, usually css is taught from a styling perspective. I found her approach quite refreshing). Anyway, I have my beginning html / css students go through these YouTubes for another great perspective on how to "think" about css.)
CSS Tutorial Pt 1 - Basic Layout
CSS Tutorial Pt 2 - Styling Links and Text
CSS Tutorial Pt 3 - Creating a Horizontal Nav
CSS Tutorial Pt 4 - Creating Boxes

2009:
A beginners guide to HTML and CSS
http://learn.shayhowe.com/html-css/

2001:
CSSZENGARDEN
http://www.csszengarden.com/ Go to this site to see the POWER of css. Click the links in the "Select a design" aside to switch to a different style sheet. Remember there is ONE and only ONE html file. But by applying a new style sheet, you can see just how powerful and flexible your web site will be when you separate style and layout from substance. Note that you can also download the html and css files to learn more!

1999:
W3 Schools online tutorials on HTML, CSS, JavaScript and more
http://www.w3schools.com/