Round corners:
http://www.cssjuice.com/25-rounded-c...ques-with-css/

3 column layout with background filled all the way to the bottom:
http://www.pixy.cz/blogg/clanky/css-3col-layout/

Vertical centering:
http://www.student.oulu.fi/~laurirai/www/css/middle/

Flash with xhtml standards satay method(so you can get valid html)
http://www.designlegion.com/rave/fla...-satay-method/

Form field hints with css and JS:
http://www.askthecssguy.com/2007/03/...h_css_and.html

CSS Opacity and Transparency:
http://www.mandarindesign.com/opacity.html

More to come later. You are welcome to add your own.