[[What is ActiveX?  Where does one read about it?]]
A good place to start might be:  http://www.microsoft.com/com/tech/ActiveX.asp

Tcl extensions that support ActiveX in some way include [ActiveTcl], [TclScript], [Optcl], [TclControl], [Noel Frankinet]'s [AxTcl] (well, not really ''his''),
[TclBridge],
...

Include tcom here, as ActiveX objects are basically lighter-weight
COM objects