Google, Yahoo! and Microsoft have announced joint support of Google's sitemaps protocol. A new site, sitemaps.org, will support the effort. Yahoo is apparently already accepting submissions, although this is not clear from their Site Explorer submission screen. Microsoft is still testing sitemaps internally.
Each of the engines should be commended for this constructive collaboration, following on the heals of noodp support.
Ask, come join the party! Don't be a spoilsport!