Great new article on A List Apart introducing on to Sass.
While browsers aren’t ready for a new CSS, Catlin and Weizenbaum (the authors of SASS, ed.) realized they could go ahead and design a new style sheet syntax with features to help make their increasingly complex CSS easier to write and manage, then use a preprocessor (a program that runs on your computer or server) to translate the new smart syntax into the old, dumb CSS that browsers understand.