I'm blogging while sitting listening to John Craddock and Sally Storey presenting one of the all-day pre-conference seminars "Stretching Directory Boundaries Cross Platform Identity Management, Authentication and Security" at the Microsoft IT Forum in Copenhagen. On screen as I write is a fantastic demonstration of ADFS (Active Directory Federation Services) which is due to be included in the R2 release of Windows 2003 server some time next year.
This is a fantastically powerful mechanism to allow cross-organisation information sharing. This type of federation is still way in its infancy. However. for a good overview, see the White Paper Active Directory Federation Services: A Path to Federated Identity and Access Management on the Microsoft web-site.