Darren's Rexx Add-ons: RxSock and RxDial, including C source code. By Darren Abbott.
dbfREXX: Database functions for dBASE, Foxpro, Clipper.
LesTec Pty Ltd: Modular And Integrated Design (MAID) for Windows and OS/2 (visual Rexx GUI) and input/output function library.
Lueck Data Systems - Solutions: Offers free ObjectCUR cross-platform utility library, including CUR for classic Rexx.
Rexx/CURL: Interface to the cURL package for access to URL-addressable resources such as web pages, ftp sites, and telnet sessions.
Rexx/Curses: Interface to Curses, a Text-mode user interface.
Rexx/gd: Interface to manipulate simple graphics images.
Rexx/ISAM: Interface to ISAM files.
Rexx/SQL: Interfaces to many SQL Databases.
Rexx/Tk: A library for using the Tk GUI toolkit.
Rexx/Trans: Rexx API translation library
Rexx/Wrapper: Build executable program from Rexx programs.
rxJava: Rexx functions for Java.