As far as starter themes go, the AdaptiveTheme is both flexible, robust, and has dozens of options within the admin interface for changing the layout and other site features. It also comes Skinr-ready.
However, it was lacking one minor feature, which is usually desirable in most designs. The sticky footer.
Adding a custom region to any Drupal theme is fairly easy. For this example, I'm working within a Zen Ninesixty subtheme. I decided that instead of just using the right sidebar, I wanted to have a custom region inside the main content area so that the text would wrap around whatever I placed here. (By default, the main content area does not wrap around left or right sidebars.)
For all the hype this theme has received, I would have guessed it was created by Steve Jobs himself. Every blog post, review, and so-called "how-to" explains why a grid system is highly preferable, how it will streamline your designs, how it will change your life and make you pancakes for breakfast, etc...