Google launched a new open source Google Sitemap Generator Beta, a server plug-in that can be installed on both Linux/Apache and Microsoft IIS Windows-based servers. It finds new and modified URLs based on your webserver's traffic, its log files, or the files found on the server. By combining these methods, Google Sitemap Generator can be very fast in finding these URLs and calculating relevant metadata, thereby making your Sitemap files as effective as possible. Once Google Sitemap Generator has collected the URLs, it can create the following Sitemap files for you: “XML Sitemaps, Mobile Sitemaps, Code Search Sitemaps”.
It can also send a ping to Google Blog Search for all of your new or modified URLs. You can optionally include the URLs of the Sitemap files in your robots.txt file as well as "ping" the other search engines that support the sitemaps.org standard.