CSS Ratiocinator - A tool that will automatically refactor your CSS
Optimse your CSS. A new take at an old issue.
CSS3 Please! The Cross-Browser CSS3 Rule Generator
You can edit the underlined values in this css file but don't worry about making sure the corresponding values match, that's all done automagically for you.
LESS - Leaner CSS
LESS extends CSS with variables, mixins, operations and nested rules
zen-coding
Set of plugins for HTML and CSS hi-speed coding