Apart from the two implementation described in the Introduction, there are many applications writte n in Tcl/Tk or a combination of Tcl and C. A complete list where to look for these implementation is the part 4 of the frequently-asked questions on Tcl/Tk (FAQs). I suggest you to visit
Scriptics' Softwar e Central.
Another good starting point is www.NeoSoft.com/tcl/.
One of the best Tcl applications running under Linux is called TkDesk a window manager and application launcher that works very well.
If you're a Tcl/Tk Linux developer, feel free to send me a URL (and a description of the work) that I can link to in here.