These are the slides I used for the MagentoWA talk about Sass, Compass, Bundler and their integration with Magento themes to manage styling for a large site.
Magento Themes and Sass/Compass is a powerful combination. You can use Compass's
add_import_path directive to include partials from your default theme, and use the theme asset inheritance to include your new
style.css without writing any layout XML.
Modern tools for Magento development Part 2