i think standalone sitemap generator is the best tool around to generate xml sitemaps. http://xml-sitemaps.com these days, hosting companies have got tie-ups with some 3rd parties that help you generate sitemaps for FREE... similar to xml-sitemaps.com's tandalone genrator worth 20$
If you use wordpress you can use google sitemap generator plugin. Its very simple to use, else please do it using googles Webmaster Tools.
our sites have many dynamic pages, we develop a custom php script for every site who generating the sitemap automatic and a cronjob take care about the update
It has a limit of 500 pages. It is not appropriate for large sitemaps. They have a paid option for more than 500 pages, however, its not a good value for money.
A know a lot of hosting companies now offer a site map generator as part of their standing Control Panel.
You can use the the FREE site map generator tool and sitemapdoc.com is a good website to generate xml, txt as well html sitemap. I have used
i am using paid version of http://www.xml-sitemaps.com/. to generate big site maps. and it work great for me.
I have used gsitecrawler, even though it is free, it takes a lot of recourses from the computer you are using. IMHO i have to agree with everyone else XML-SiteMaps is definitely one of the best. they have a bunch of different version to fit your needs... and heck one of the versions is free. give them a try a before you try any other.