TechLookz

A site map is a graphical representation of a web site. This helps visitors and Search engine spiders to find pages on the site.

Sitemaps are particularly helpful if:
Your site has dynamic content.
Your site has pages that aren’t easily discovered by Googlebot during the crawl process - for example, pages featuring rich AJAX or Flash.
Your site is new and has few links to it. (Googlebot crawls the web by following links from one page to another, so if your site isn’t well linked, it may be hard for us to discover it.)
Your site has a large archive of content pages that are not well linked to each other, or are not linked at all.
Benefits of sitemaps

Site Map can improve Seo ( Search Engine optimization ) of a site by making sure that all the pages can be found.And it will be Easy for Search engine spiders to index the site map it will be in organized way.
Types of sitemaps

HTML page sitemap

XML Sitemaps

Submission of sitemap to Google information can be Found here

http://www.google.com/support/webmas...n&answer=40318