Google webmaster tools lets you submit your sitemaps and gives quite a bit of useful data on the pages submitted, maybe even pages that don't exist because there are link errors in your site pointing to your own internal files instead of online site pages. Information that may seem trivial but can definitely improve a site are warnings about duplicate meta-tags, unreachable pages, bad links, and how the Google search bot views your site inside and out.

One tool that helps with sites built using a common template are the warnings about duplicate meta-tags. It easy to miss replacing certain attributes or writing new meta data for custom pages, so using this function makes it easy to do some housekeeping and as a reminder for those forgotton changes.

Another feature is called "What Googlebot Sees". This analyzes a site's content and links from other sites and presents a breakdown of the most commonly used words and phrases in content including outgoing links plus that of incoming links from other sites as the search engine sees it. Additionally, you might find that the "Marching Band" site looks like "High School" to Google. You can make som important modifications from this information, the article Improving A Working Website With Google Webmaster Tools details exactly what is done when a working site is updated using this.