Exchange 2003 SP2
After Steve announced SP2 at TechEd Orlando and Terry blogged about it (and so did I), I've had quite a few questions about when SP2 would be released (2nd half of 2005 by the way), and some of the features in it. Well here's the link to the page documenting the features, things like the Windows mobile 5.0 messaging and security features pack, and some of the mobility management, mailbox improvements and anti phishing technologies that will be included with SP2.
There is also an FAQ about SP2 here.