On the NETTUTS.com site today there's a new tutorial about using the LESS CSS tool to get the most out of the styling of your website. The tutorial uses the PHP implementation by Leaf Corcoran to accomplish the same things as the Ruby library offers.
During a sick day a few weeks ago, I got around to something I've been meaning to look at for about a year: LESS. If anything web technology is worth a look, I promise LESS is. In this article, we'll look at the amazing power of LESS and its ability to streamline and improve your development process. We'll cover rapid prototyping, building a lightweight grid system, and using CSS3 with LESS.
They use an output buffering trick to handle parsing and executing the ".less" CSS-based files through the library and spit the parsed version back out the other side. There's plenty of examples of how to use the LESS syntax ending up in their previously mentioned grid system using mixins, some cross-browser CSS3 and the CSS3 Pie tool.