Tcl-Gtk is a project to provide Tcl with access to the libraries using the GObject type system. Tcl-Gtk focuses on Gtk and Gnome libraries. See Mmucl for an example of an app using Tcl-Gtk. Browse the documentation here.
This project is on hold for the moment. If there is some interest shown or I think of a cool app to write with it, I may work on Tcl-Gtk some more.
Available from SourceForge.