CSS Next - Use tomorrow’s CSS syntax, today.
Fossil - Simple, high-reliability, distributed software configuration management
Garden (Clojure) - Unlike the mini-languages that are other pre/post-processor options, Garden leverages the full power of the Clojure programming language for CSS.
AppDNA - AppDNA is a small XCode shell script which efficiently packages a Mac OS X Application's source...
Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS
CSS-Crush - A standards inspired CSS pre-processor. Written in PHP.