I use Tcl/Tk for 10 years. What a nice programming language ! Without Tcl, I had certainly never begin programming !
Some software I have developed :
Win-dem : an alternative desktop for Windows in school environment
Tkontrole : another software for school, which permits teacher to look at students computers screen from teacher's computer, and control them.
My new project : a software to build and simulate mechanical mechanisms in 3D...