This plugin allows the use of SASS for CSS preprocessing within Textpattern.
It will compile the SASS code you define within the regular CSS style form to static CSS files, serving it through a tag which is quite similar to the well known <txp:css /> tag.
This plugin relies on PHPSass and borrows code from the sassy module for Drupal. It started off as a hack of rvm_css, which can do similar things with LESS.
See plugin help for further details.