Less is probably the most well known CSS preprocessor. It allow a simplified syntax and the use of variables. Less CSS is for the Ruby programming language, however it looks like Aaron Russel created an extension for creating cached stylesheets your PHP projects can use.
Get it: http://lesscss.org
On their website, Sass claims to make CSS fun again. To be honest, I must admit that what this project is capable of is very interesting. Like Less CSS, it allow the use of variables and have a simplified syntax. Sass is definitely a great tool, unfortunely only available for Ruby, as far as I know.
Get it: http://sass-lang.com/
If like me, you’re a PHP Lover, here is a css preprocessor made for your favorite language. I haven’t tested it yet, but Turbine looks very cool. It allow a minimal syntax, automatically gzip multiple css, fix cross-browser issues, and a lot more. A must check if you’re into PHP.
Switch is a full featured, production ready CSS preprocessor. It runs under Apache with mod_python, or as an environment-agnostic command line tool.
Get it: http://sourceforge.net/projects/switchcss/
CSS Cacheer is a very cool preprocessor which allows developers to create plugins. It requires PHP and Apache with mod_deflate and mod_rewrite in order to work.
Get it: http://retired.haveamint.com/archive/2008/05/30/check_out_css_cacheer
Another interesting preprocessor, written in PHP 5. Among other things, this tool allow you to use expressions such as margin-left: (200px * 3/2 – 10px); in your stylesheets.
Get it: http://pornel.net/css
DtCSS speeds up CSS coding by extending the features to CSS. Such as nested selectors, color mixing and more. DtCSS reads the CSS file with special syntax written for DtCSS, and outputs the standard CSS. It also comes with a smart caching system.
Get it: http://code.google.com/p/dtcss/
Unfortunely, CSS PP is still in alpha status, but the authors says the code will be released very soon. One of the good points of this projects is that it will be available in PHP, Python and Ruby. Great news for developpers who work with all of these languages.
Get it: http://csspp.org/