Cube is a clean admin theme for Drupal 7. It comes with several regions and layouts, a set of icons for admin pages provided by Drupal core and an aggressive styling to reduce visual noise wherever possible.
For having sidebar columns you will need to use Conext Layouts.
- Has Fixed/Fluid page widths.
- Works good with Drupal 7 Overlay.
- Works good with Conext Layouts
- Integrates with DesignKit
Cube on Drupal 6 is not going to be supported here in the mean time. You can find it within Rubik package for Drupal 6.