Some cool stuff here...
http://meyerweb.com/eric/css/
Lot's of good stuff here...
http://css.maxdesign.com.au/index.htm
Some decent links here...
http://www.mezzoblue.com/zengarden/resources/
alistapart.com is good too.
I suggest getting the Web Developer plugin for Firefox. It has a ton of great features and is quite helpful when working with CSS (the css editor is nice and the Outline tools are especially helpful).
Most importantly, trial and error. Good luck.
