Colin Devroe has started an interesting series of posts on the topic of how 9rules.com was built. The first in the series looks at the early days and how they used WordPress to accept submissions and add new blogs to the network. This promises to be an interesting series to keep an eye on.
Problogger.net runs on the Genesis Framework
The Genesis Framework empowers you to quickly and easily build incredible websites with WordPress. Genesis provides the secure and search-engine-optimized foundation that takes WordPress to places you never thought it could go.