I'm a family doctor and amateur Tcl programmer. I put together a
program called <a href="http://www.psnw.com/~alcald/#informatics>Tkfp</a>I use in my office daily to manage the medical records on my 
patients. I've used many of the wonderful Tcl extensions (tclxml, Incr Tcl, tkhtml) and embedded a number of great Tcl/Tk applications (tclhttpd, plume, impress) by the people on the Wiki into my program. I wrote some of my own code to organize these and make them work together in a useful way for a medical practice.  I'm currently working on medical EDI - electronic data interchange (ANSI 837 v4010) format that Medicare and other Medical Insurance Co's in the U.S. use to transmit medical claims data. If anybody has experience with this area and would like to help, I would really appreciate it. I also did a project for a doctor friend that displays an interactive medical decision making algorithm in a Tk canvas widget. The output from interacting with it goes directly into the patient's  medical record. We call it "MedMapper". It uses object oriented programming and you can edit the algorithm while the program is running without knowing anything about programming. It can save it's current state for the next session.

I'm not a good enough programmmer to contribute anything new to Tcl/Tk but I did have a couple of Tclets that were used as demos for the Tcl plugin on the plugin's web site.  I did have a little thing published on the Scriptics Developer site about  "rendering" XML into a Tk text
widget by mapping the XML tags using text widget marks and tags. It works pretty well in my app. I can edit the xml data right in the text widget and it all gets stored in the background as XML.