A quick scan of sourceforge gives a bunch of projects whose name begins with tcl. I'm going to trawl through them all. Around a hundred. Who knows what we'll find.
Project front pages
Projects with no front page
Projects that are Tcl based without a Tcl prefix
Here are some to check out
Are you using sf.net's search engine to search for tcl? I don't know if there are also projects which use tcl but which don't have tcl in the search description.