http://www.web-design-pros.ca/software/sitemapGenerator.html

Another free xml based sitemap generator based on java platform from web design pros. It creates sitemap specifically for google. This tool has capability of generating 50,000 links which is good for web sites having dynamic content

To use this tool enter web URL in step 1 tab, and then click start button it will show the progress status in bottom bar. Under tab step 2 you can see actual URL list that has been fetched and an option to generate xml file. Finally in tab step3 when the list is ready you can directly upload your sitemap to your FTP server and then ping Google to inform about it.