YOu will be able to exchange free/busy information across forests using the new Availability web service in Exchange 2007, but not calendar details. Users can send calendar details (using iCalendar) to either other easily, though, with Outlook 2007.

--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx

"Tom - UofA" Tom - wrote in message ...
Hello,

I have a situation where it would be really useful to be able to share
Calendars across different Active Directory forests. While it is not
currently possible, will this be enabled in Exchange 2007? (If someone knows
how to do this in Exchange 2003 - please post the details).

Thanks

TG