By placing a Sitemap-formatted file on your webserver, you enable the Google crawlers to find out what pages are present and which have recently changed, and to crawl your site accordingly.
It's very important to have a Site Map so search engines can find all of your pages. Also many of your visitors use Site Maps to navigate your Website to get where they need to go instead of looking for links.
SiteMapper will analyze the contents of a web site, and create a detailed map with an indexed listing of all resources by page and category.
Trellian SiteSpider is a powerful, yet simple to use sophisticated search, web crawling and site mapping tool.
SiteMap XML - Dynamic SiteMap Generator, is a php based sitemap generator. It includes a range of configurable variables and can be run as an online form or in automatic xml mode to create real time dynamic site maps.
Generate sitemaps for your website, be that HTML or XML Google sitemaps. Rich template support for generating sitemaps and near-endless scanning options. The scanning engine stores website data so you can view reports on broken and redirected links.
Site Map Pro - Create a site map for any website