I'll come back soon and add images and links that are germane to Tcl. In any case, we are writing what is very nearly an operating system in Tcl, with C++ extensions wrapped using SWIG.
http://www.ligo.caltech.edu/LIGO_web/about/
Ah, ok, I'm back!
The Laser Interferometer Gravitational Observatory Data Analysis system (LDAS) is a heterogeneous colection of computers running Linux (x86 and Alpha) and Solaris (Sparc boxes). There are thousands of boxes arranged in various configurations ...
To be continued
See also Phil Ehrens.