I noticed that Jason's (http://blogs.msdn.com/thehoggblog/archive/2007/08/20/swiss-army-knife-of-x-509-certificate-tools.aspx) and Justin's (http://blogs.msdn.com/justinjsmith/archive/2007/07/10/new-wcf-security-examples.aspx) blog entries refer to an old location at http://wcf.netfx3.com that seems to be down. I figured out that the tool is now available for download from the WCF community samples here: 

http://code.msdn.microsoft.com/Project/Download/FileDownload.aspx?ProjectName=netfxsamples&DownloadId=3395