Here is something i just recieved in an email, its a tutorial on how to build a google sitemap or something, it mite or mite not be useful for you. http://www.seoelite.com/Demos/GoogleSitemap.htm
I think is very useful for beginers. But how does that program know which threads should have a higher priority? I made a script that sets priority for each thread on forum, depending on number of messages, and the "age" of threads. Anyway, I don't see any result.
This online one is very good. Don't know about forum threads though. The best would be to set up a serverside one and a cron job that submits the sitemap every hour or something. http://www.auditmypc.com/free-sitemap-generator.asp
Well, if you are using Mambo for your content management, I have an add-on that acts as the sitemap. Available at http://mambo.medspan.info/downloads under the 'Useful Mambo Add-ons' folder...
Sure it is very helpful for beginners but I prefer to make my sitemap manual because it would be perfect for search engines.