My biggest Tcl/Tk project sofar is the complete reverse engineering and rewrite of the visual basic software for the HomeVision [L1 ] home automation controller. In addition to running on multiple platforms, I've added some features that the original software was lacking.
I get great support from the President of Custom Solutions, Inc. However he doesn't like me to release the source code, so I had to use procomp to obfuscate the code. The project does provide plain Tcl plugins and allows users to write their own plugins. As a result I have already introduced two other homevision users into the wonderful world of Tcl. Hopefully more will follow.