Rexx/ISAM
- Interface to ISAM files.
- http://rexxisam.sourceforge.net/

rxJava
- Rexx functions for Java.
- http://rpm.pbone.net/index.php3/stat/4/idpl/56083/

Rexx/CURL
- Interface to the cURL package for access to URL-addressable resources such as web pages, ftp sites, and telnet sessions.
- http://rexxcurl.sourceforge.net/

Rexx/Curses
- Interface to Curses, a Text-mode user interface.
- http://rexxcurses.sourceforge.net/

Rexx/Wrapper
- Build executable program from Rexx programs.
- http://rexxwrapper.sourceforge.net/

LesTec Pty Ltd
- Modular And Integrated Design (MAID) for Windows and OS/2 (visual Rexx GUI) and input/output function library.
- http://www.lestec.com.au/

Rexx/gd
- Interface to manipulate simple graphics images.
- http://rexxgd.sourceforge.net/

dbfREXX
- Database functions for dBASE, Foxpro, Clipper.
- http://www.dsoftusa.com/dbfrexx.htm

Rexx/SQL
- Interfaces to many SQL Databases.
- http://rexxsql.sourceforge.net/

Rexx/Tk
- A library for using the Tk GUI toolkit.
- http://rexxtk.sourceforge.net/

Rexx/Trans
- Rexx API translation library
- http://rexxtrans.sourceforge.net/