Sass and LESS were both introduced in 2009. Since then, both meta-languages have exploded in popularity. Both Sass and LESS allow you to write elegant and reusable CSS in a third of the time it would normally take using standard flat CSS.
In this webinar I will walk through a handful of useful concepts and key differences between the languages. Drupal has several modules such case LESS and Sassy that will help you quickly get up and running using either project.