UPDATE: I have since moved these articles to my own blog and they can be found here.
My second article on integrating Windows Communication Foundation with BizTalk Server is now online. The one deals with all the various WCF security configurations and how BizTalk consumes each one.
Specifically, I address message vs. transport security, certificates, username tokens and declarative code-based security. It was pleasing to see how gracefully BizTalk accommodated each security permutation I threw at it.