The BizTalk Server Developer Center has been updated to highlight integration with WF and WCF. Finally Microsoft has written a view articles on how they will include and use WF an WCF in BizTalk. Some things of BizTalk will cover the same features (e.g. BRE is very close related to WF).
Reference Application Pack for Retail
This white paper, along with the sample application, showcases integration using service orientation with BizTalk Server 2006, Windows Communication Foundation, and Microsoft Business Scorecard Manager.
Windows Workflow and BizTalk Server 2006 Code Sample
This sample demonstrates how to integrate Microsoft BizTalk Server 2006 and Windows Workflow Foundation through Web services.
Windows Workflow Foundation Overview
Windows Workflow Foundation is the programming model, engine, and tools for quickly building workflow-enabled applications on Windows. It consists of a namespace, an in-process workflow engine, and designers for Visual Studio 2005.
Hopefully MS will give us some more samples on how to use it in a production environment.