What is a wordpress theme framework?
A theme framework is a theme that is designed to be a flexible foundation that can serve as a parent theme for building child themes. The use of theme framework may ease theme development by reducing the volume of work which may be needed in creating a backbone for your theme.
Available Frameworks

Sandbox (Scott’s page)
Thematic (Ian’s page)
WP Framework (Official page)
Hybrid (Official ?age)
Carrington (Official page)
The Buffet Framework (Official page)
WP Basis (Official …