Now you can submit to 50,000 (a URL or link to child Sitemap) in sitemap.xml file index. Until recently Sitemap Files only about 1,000 children left. This increase will be very useful for very large events, as is currently the only major Sitemap index file, referring to 50,000 child Sitemap files, each reference to 50,000 URLs, you can link to a total of 2.5 billion addresses.

slight change in the sitemap XSD schemas helps developers and Maps page to check the contents of the defined types. For example, attribute lastmod now XSD: date, place XSD: string. Our goal is to improve the quality of site maps to this change. Note that the sitemap schema version is still marked as version 0.9.

http://googlewebmastercentral.blogspot.com/2009/06/update-on-sitemaps-at-google.html

http://www.ysearchblog.com/2009/06/11/sitemaps-update/

http://www.bing.com/community/blogs/webmaster/archive/2009/06/12/bing-enhances-support-for-large-sitemaps.aspx