Less.js: LESS extends CSS with dynamic behavior.

LESS extends CSS with dynamic behavior such as variables, mixins, operations and functions.
LESS runs on both the client-side (IE 6+, Webkit, Firefox) and server-side, with Node.js.

http://lesscss.org/

http://en.wikipedia.org/wiki/List_of_stylesheet_languages
http://en.wikipedia.org/wiki/LESS_(stylesheet_language)