You can participate in the Google Sitemaps program by following these basic steps:

1. Creating a Sitemap in a supported format.
2. Submitting that Sitemap to Google.
3. Updating your Sitemap when your site changes.

http://www.google.com/webmasters/sitemaps/docs/en/about.html

Viewing statistics for your site

Once you have submitted a Sitemap for your site, we make statistics available to you about the URLs contained in your Sitemap as well as other URLs for your site that we discovered through our standard crawling process. ...

http://www.google.com/webmasters/sitemaps/docs/en/stats.html

Google Sitemaps is intended for all site owners, from those with a single webpage to companies with millions of ever-changing pages. If either of the following are true, then you may be especially interested in Google Sitemaps:

•You want Google to crawl more of your pages.
•You want to be able to tell Google when content on your site changes.

What is the Sitemap Protocol?

The Sitemap Protocol is a dialect of XML for summarizing sitemap information that is relevant to web crawlers. For each URL, you can include crawl "hints" like the last modified date and approximate change frequency. You can read more about the Sitemap Protocol here.

http://www.google.com/webmasters/sitemaps/docs/en/faq.html