Which Drupal 6 theme framework is good for creating a responsive web design? Which Drupal 6 theme framework is good for creating a responsive web design? Is it advisable to use Zen starter-kit to develop a responsive theme?
Omega offers good responsive features. 
"Fully Responsive Grid layouts based on 960.gs standards."

I have used this for many 7 projects but not tried 6, if this is a new project you are starting I would recommending starting with 7.