There are a handful of WordPress frameworks out on the inter-tubes. They are used like frameworks for other platforms – in WordPress they speed development of themes.
Being that most of us are working against multiple deadlines at one time, we need to be able to save ourselves as much time and headache as possible, and help prevent ourselves from unnecessarily re-inventing the wheel. That is why frameworks are such a time and life saver in the development arena. (Actually, frameworks are simple time savers regardless of whether or not you are facing a deadline.)
Here are six of the most popular from Pro Blog Design.