A few weeks ago Microsoft released an updated version of the documentation for BizTalk 2006.
You can download the updated docs here.
The new content has some really good stuff including:
- Complete documentation for all BizTalk Server Line of Business Adapters, including new tutorials, one for each adapter. See the section "Using Adapters."
- Disaster recovery instructions for backing up and restoring your BizTalk Server and databases. See the section "Backing Up and Restoring BizTalk
Server"
- Information for improving fault tolerance. See the section "Planning and Architecture"
The only thing is the download is over 40 MB and it is in .chm format. So, this will not replace your existing BizTalk Documentation but rather provide you a second full version of documentation. Not sure why it is packaged like that...