Google Sitemap Generator
If your not so keen on generating your Site-maps by hand, I suggest you use a tool that I found last month and got completely addicted too.
It’s an absolutely fantastic script that crawls your internal links, detecting 404 erros, pages with duplicate content, invalid redirects, and much more.
After validating the links, you get to choose the update rate and priority of each page and then simply finalize by generating your XML.