In this fairly long video a Google Engineer talks about how to set up and configure URL parameters in the Google Webmaster Tools control panel. Although this video is not for every website, owners of websites that pull data from a database and have an e-commerce website will definitely want to watch this important video. It talks about how to filter out pages dynamically generated by your application that may create duplicate pages that Google may spider which may not be a good thing.
From McCord Web Services – Google Partner and Web Visibility Experts