Check out my thread here: http://forums.digitalpoint.com/showthread.php?t=958367 This is free, unlimited and will auto add new pages daily.
Google recommends that sitemaps submitted to them do no exceed 50000 links. Read http://www.google.com/schemas/sitemap/0.84 for more information. I have a small and simple sitemap generator at http://www.webrickco.com/buildsitemap.php. It is limited to 10000 links, but i can raise it if you want to make the test. I will also help you in case of troubles. PM me if you are interested.