BREXX
   Free interpreter for Unix, MSDOS, WinCE and Amiga. By Vassilis N. Vlachoudis.
   http://ftp.gwdg.de/pub/languages/rexx/brexx/html/rx.html

BeBRexx
   BeOS port of BREXX.
   http://www.bebits.com/search?search=rexx

CICS Rexx
   Language and development environment.
   http://www-306.ibm.com/software/htp/cics/products/rexx/

Jaxo: Rexx for Palm OS
   Product description, including downloads and free runtime.
   http://www.jaxo.com/rexx/

KEXX
   Dialect used in KEDIT (XEDIT-like editor). Summary by Rex Swain.
   http://www.rexswain.com/kedit.html

REXX/VSE
   Product page, including support information and samples.
   http://www-03.ibm.com/servers/eserver/zseries/zvse/support/rexx.html

REXX/imc
   Open source Rexx interpreter for Linux/Unix.
   http://users.comlab.ox.ac.uk/ian.collier/Rexx/rexximc.html

Rexx Anywhere
   Writing portable Rexx execs. By Dave Alcock.
   http://www.planetmvs.com/rexxanywhere/

S/REXX
   UNIX implementation from Benaroya. Graphical debugger available.
   http://www.sedit.com/rexxgrph.html

r4
   Classic Rexx language interpreter for Windows, from Kilowatt Software.
   http://www.kilowattsoftware.com/r4Page.htm

uni-REXX
   An ANSI standard implementation for UNIX systems. Free sample code library.
   http://www.wrkgrp.com/unirexx/