BizTalk Server 2006 R2 Posters
At BizTalk booth in TechEd Developers 2007 in Barcelona, we had some large posters displaying the capabilities and architecture of BizTalk. We distributed many paper copies of these posters at the conference.
Those posters are available for download.
I think these posters do a good job at somewhat "whiteboxing" the mystery of BizTalk Server. :-)
You can find more information about these posters at BizTalk Server Team Blog.
