Ruby

Compass is a stylesheet authoring framework that makes your stylesheets and markup easier to build and maintain. With compass, you write your stylesheets in Sass instead of CSS. Using the power of Sass Mixins and the Compass community, you can apply battle-tested styles from frameworks like Blueprint to your stylesheets instead of your markup.

It’s a Ruby on Rails project. You run a CLI utility that watches a directory where your .css and .sass reside. The changes you make to your .sass files get automatically parsed and translated to .css files. The .sass format allows you to have a simplified less repetitive stylesheet markup, in addition to the ability to use variables, functions, mathematic operations, and more.

• In CSS, ever wished you could store the color palette for your site design in a few variables and then just reference those variables through the stylesheet?
• Ever wished you could perform cross-browser compatible mathematical addition on layout column widths?
• Ever wished you could easily gather a library of commonly used CSS, and then selectively include them in your various designs with a single line?

Now you can, with Compass.

Installation on Debian/Ubuntu 9.10 Karmic is like:

sudo aptitude install ruby gem; # dependencies
sudo gem sources --add http://gems.github.com/
sudo gem install chriseppstein-compass; # install
sudo gem install chriseppstein-compass-960-plugin; #optional plugin
compass -f blueprint project; # example usage
compass -r ninesixty -f 960 project; # example plugin usage

Looks promising! See more detailed Compass install instructions.