We now provide sitemaps for all Wikimedia wikis. The sitemaps can be found at http://sitemap.wikimedia.org/sitemap/
Sitemaps are XML lists of all the pages in a website. We also provide the last-modified timestamp for each page and a "priority". We use a high priority for articles and lower priorities for the other namespaces.
In mapping.txt there's a mapping from website name to the URL of the sitemap. The sitemaps are split by namespace, so if you're only interested in one namespace, you can get it without downloading the rest of the files.
A descirption of the XML schema is available at http://www.google.com/webmasters/sitemaps/login?sourceid=gsm&subid=us-et...
If your application uses our sitemaps we'd be happy to hear about it.
Regards,
JeLuF