I read in my SEO book that a sitemap is a good thing to have for a website. Though it doesn’t directly impact ranking, it does make sure a search engine can index all your web pages. I look at a couple and liked XML-Sitemaps.com.
The sitemap tool is very easy to use. First you type in your website URL and click the Start button. It goes through your site and generates the XML file which you can then upload via FTP to your website. You then go into Google Webmaster Tools and tell Google where to find the file.