I just found this free course on MSDN, amongst others that are offered for free.  I am in the process of getting smarter on BizTalk 2006, so that I can understand it from an SOA perspective and have been looking for as many free resources to help me get there as I could find.

If you are interested in understanding the basics of BizTalk 2006 from a Developers perspective, this online course is an adequate starter and I would recommend it before delving into any more expensive options.  It will give you the background that you need before taking a more advanced course.

Here's the description and objects (from the site):

Title: Clinic 2954: First Look: Microsoft® BizTalk® Server 2006 for Developers

Course Type: Self-paced Course

Estimated Time of Completion: 3 Hours

Description:
This online clinic provides developers with an introduction to the BizTalk Server 2006 development environment and BizTalk messaging and orchestration services. This clinic also highlights BizTalk features and functionality through demonstrations of common developer tasks.

Objectives:
At the end of the course, students will be able to:

  • Describe the services and tools provided in BizTalk Server 2006.
  • Describe the BizTalk development environment and toolset.
  • Describe the purpose of a BizTalk schema and how to create a schema.
  • Describe the purpose of a BizTalk map and how to create a map.
  • Describe the purpose of a pipeline and how to create a pipeline.
  • Describe how BizTalk applications are deployed.
  • Describe the purpose of an adapter and how an adapter is configured.
  • Describe how BizTalk orchestrations work.
  • Explain schema promotion and how it works.
  • Describe the types of transactions that can be created in an orchestration.
  • Explain how Web services can be integrated into an orchestration.
  • Describe how messages can be monitored in BizTalk.

Here's the link: https://www.microsoftelearning.com/eLearning/courseDetail.aspx?courseId=51883

Enjoy,

~ Robert Shelton