When it comes to search engine visibility the sitemap.xml file as well as a page that includes your site map are really important. These files allow search engine crawlers to have a finely indexed map of your website, the easier you make it for the crawlers, the more they'll like your website. Also a few tools such as Google Webmaster Tools allows you to upload a sitemap.xml file for better visibility.
Don't have Google Webmaster Tools added to your website tool kit? Found how to create a Webmaster Tools account and add your website easily!