There are free sotwares to create Google Sitemaps:
Web based: http://www.blocklayer.com/googlesitemap/ (it is a little bit hard to update the sitemap manually as you add more pages to your site)
Program: http://www.vigos.com/products/gsitemap/ You can download it and it crawls your pages, makes the sitemap and upload it to your server. And you only have to resubmit the sitemap to Google (but in my experience, you don’t have to do it, G makes it periodically).