Google, Yahoo and Microsoft have agreed on a standardized Sitemaps-protocol. Microsoft is still taking some time while Google and Yahoo have already implemented the Sitemaps. The protocol builds upon the draft of Google Sitemaps, which means that users who already create Sitemaps for Google will only have to register them with the other searchengines. Further informations can be found at sitemaps.org. I think this is a very sensible step that the searchengines are not all going with their own proprietary Sitemaps-specification. We have already seen that the three large searchengines can work together with the introduction of the Nofollow-attribute.