Windows Workflow Foundation
In PDC 05, Microsoft unveiled the Windows Workflow Foundation (WWF) a programming model for building workflow enabled applications. It bolts on Visual Studio 2005 and adds some designers and some new namespaces. Slated to release by mid 2006, you can use this right now under Windows Server 2003 SP1, Windows XP SP2 and Windows Vista. You will need Visual Studion 2005 Beta 2.
Looks pretty cool and I've started playing around it. Will blog more or better still, take a session at B.NET or write an article about it.