Many of these were released a few months ago in a beta form but now they are available on the Microsoft website.
They include the following:
BizTalk Server 2004: A Messaging Engine Overview
BizTalk Server 2004 and Web Services
Connecting to the Elemica Network with BizTalk Accelerator for RosettaNet 3.0
Developing Integration Solutions with BizTalk Server 2004
Implementing UAN on BizTalk Server 2004 to Integrate Siebel and SAP
Risk Scoring with BizTalk Server 2004 and the Business Rules Framework
Transactions Across BizTalk Server 2004
Working With BizTalk Adapter for SQL Server
BizTalk Server 2004 Convoy Deep Dive
They all look like great reading!
In addition, I have finally gotten around to getting my website up and running. It still needsALOT of work, but at least it lists all my BizTalk samples, tools, and demos in one place. Check it out at http://www.biztalkgurus.com