The Sitemaps protocol allows a webmaster to inform search engines about URLs on a website that are available for crawling. A Sitemap is an XML file that lists the URLs for a site. It allows webmasters to include additional information about each URL: when it was last updated, how often it changes, and how important it is in relation to other URLs in the site. This allows search engines to crawl the site more intelligently. Sitemaps are a URL inclusion protocol and complement robots.txt, a URL exclusion protocol.
How to Add a Google XML Sitemap to Your Web Page
Introduction to Video Sitemaps
SEO - How to create a simple Sitemap
Google I/O 2008 - Sitemaps: Exposing Content in Web Apps
How to Easily Add A Sitemap.xml File to Your Website
Which is better: an HTML site map or XML Sitemap?
How to create and submit an XML sitemap using free tools
Google Sitemaps