The Microsoft case study site is a collection of easily-digestible executive-style summaries of people using Microsoft products. While ordinarily this may not sound all that interesting, case studies are good sources of easily stealable material whenever someone asks you to justify why you're using a particular technology. Of course, finding the case studies about WCF in the collection is next to impossible as WCF is not in the case study product list and all of the relevant keyword searches produce either far too few or far too many results to be what you're looking for.
Rather than making you search for case studies, I have a selected collection of case studies that deal strongly with WCF. I have filtered these case studies so that they all were published around the time that WCF was finished or later. Obviously though, many of the case studies will be based on prerelease software as it takes a considerable amount of time to complete a project and then complete the case study.
Tax and Accounting
Fire and Security
Next time: ChannelFactory Behaviors