haml

I’ve not used Haml for anything ever, but I have used Sass for sites that I’ve coded by hand, though not with Drupal. With that in mind, I also haven’t watched these presentations, but I do remember the first one getting a lot of excited buzz at DrupalCon Chicago. Finally if you grow to love Sass, look into using the Compass CSS authoring framework that builds on Sass and makes it even more amazing:

http://compass-style.org/

The following presentations were made at the past two DrupalCons in the US:

DrupalCon Chicago 2011
Themeing Haiku with Haml, Sass, and Peroxide.

Hey Everyone,
May I introduce you to Peroxide an in-development Drupal theme engine that uses Haml as a templating language and can use Sass stylesheets. Peroxide's goal is to make themes faster and easier to create, and to make them more maintainable over time. Haml and Sass both present nice abstractions and tools to make working with templates and stylesheets respectively much easier. Peroxide is also bundled with the compass styling framework which makes it extremely easy to import existing CSS frameworks including Blueprint, CSS resets, CSS3 compatibility tools, and more into your theme.

For any fans of Haml out there, I've submitted a filter module that leverages phpHaml: http://drupal.org/project/haml