Several years ago I wrote a turbo Pascal 3 based HL7 v2.X parser. I have since learnt a lot but the basic parsing code has always worked. So, now that I am working at Microsoft I have redone the code yet again - this time in C# and WPF and released it to: http://code.msdn.microsoft.com/HL7v2parser.
I will make more enhancements now as I am getting up to speed on the whole WPF, IIS, BizTalk and C# stuff so stay tuned.