Here's a thoughtful webcast talk about 'lean start-ups':
Lean start-up is not limited to your traditional start-up company. Rather, it can also refer to a small department in a large company. Essentially, the speaker, Ries, believes that an effective lean start-up can be boiled down to rapid releases. Ries suggests a couple of techniques to get to rapid releases. One of the more radical technique is continuous deployment where source check-ins that pass integration tests are deployed automatically. Of course, there would need to be a mechanism in place to revert back quickly. Ries also describes split testing where new features are tested in parallel with existing code, essentially a control and experimental group comparison. Ries also recommends asking the 5-why's on every issue (e.g., asking why did this bug occur 5 times at different level from the programming level to the management level).
This talk is worth the hour if you are interested in improving your development process.