Stylecow - CSS processor to fix your css code and make it compatible with all browsers
Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS
CSS Next - Use tomorrow’s CSS syntax, today.
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.
PostCSS - Increase code readability. Add vendor prefixes to CSS rules using values from Can I Use. Autoprefixer will use the data based on current browser popularity and property support to apply prefixes for you.
Sass - Syntatically Awesome Style Sheets