X09 Theme is a highly extensible, minimal theme for Drupal 6, it is built on top of a blueprint css framework to help maintain consitency and make it easier for developers/designer to customize.

it has also the Cross Browser Drop-Down framework to render the primary links.

To find out how you can build on X09 theme, you can check this demo site : http://www.smsar.me

X09 is now FREE you can proceed with $0 checkout of you can just download it from github