SS 2004-02-10: I used the last weekend to implement Joy in Tcl. It's not very fast of course, and still not complete, but does tail call optimization, has first class continuations, and is stackless (The interpreter never call itself), so it's simple to transfer an entire running program from an interpreter to another one.
Too big to put it here on the Wiki, so download it from http://www.hping.org/tclsbignum/joy.tcl if you are interested.
Run it with
tclsh joy.tcl
to use the interactive mode, or pass an file name to execute a program written in Joy.
As stated, it's still not finished. Many primitives are missing, but can easily implemented in Joy itself. Also note that currently the 'set' data type is missing.
Use the help command to print a list of the defined words.
I plan to have a fully compatible interpreter in some day.