Child themes are one of the most useful features that as a developer thinking about using Drupal or WordPress or want to get a little bit more control of your layout and theme development needs to no.
What is a Theme Framework? If you want to design and develop your own theme from scratch but want to have access to the full power of plugins and widgets (wordpress), and modules (drupal) then a theme framework is for you. The problem is you don’t want to go into the core code of the theme files and start making changes only to have something go wrong and you loss everything or you need to upgrade. So this is when Child Theme come in!
A Child theme utilizes the power of the parent Framework files but give you the freedom to build in a separate folder as to not muck up the core.
For now here is a list of great resources to get you started.
Thematic, A WordPress Theme Framework.
Blank Themes, Frameworks and Templates: Resources to Speed Up Your Development Time – Web Design Blog – DesignM.ag.
Zen Framework | drupal.org.
Zen nineSixty (960 Grid system) | drupal.org