Google Webmaster Central Blog has a new post explaining the best practices for using XML Sitemaps and RSS/Atom Feeds.

Best practices for XML sitemaps & RSS/Atom feeds

Submitting sitemaps can be an important part of optimizing websites. Sitemaps enable search engines to discover all pages on a site and to download them quickly when they change. This blog post explains which fields in sitemaps are important, when to use XML sitemaps and RSS/Atom feeds, and how to optimize them for Google.