Located at http://www.sys.uea.ac.uk/~fuzz/TclControl/default.html and written by Farzad Pezeshkpour.
TclControl is an ActiveX control that exposes Tcl and Tk to ActiveX containers such as Visual Basic, Internet Explorer, MFC and others. The control provides methods for evaluating scripts and accessing Tcl variables. It also provides callback events for Tcl variable tracing. The current release is version 2.0 build 03. You can download it from here (76KB). You can download a couple of screenshots from here also: one with Internet Explorer and one with Visual Basic.
New! Replacement for TclPlugin for Internet Explorer Gary Lee has kindly patched TclControl so that it can interact same way as the Tcl Plugin. You can get the patched version from Gary's page.