Commercial Products
IBM Compiler and Library for REXX on zSeries, MAX Software, Relational Architects International: Rexx Language, REXXTOOLS/MVS, RtoR - REXX to RACF
Documentation and Tutorials
Dave Matthews, FAQ for TSO/REXX, REXX for CICS/ESA, REXX Under CICS User Experience, REXX/370 Compiler and Library, REXX/VSE, Sysprog.net: REXX for OS/390, TSO/E REXX Manuals, ÜberFish Style Guide for Rexx, VM/ESA REXX Manuals
Scripts
A few ISPF or OS/390 Tools and Toys, BGD Software, Bill Lalonde - Big Iron, Capitalware's Sample OS/390 Code, CBT Tape, Dave's MVS freeware - Rexx, David McRitchie: The REXX Macros Toolbox, Frank Clarke: REXX/MVS code examples and utilities, GSF Tools & Docs, ISPF Edit macro examples
VM and VSE
CMS/TSO Pipelines, REXX Workshop, REXX/VSE, REXXTOOLS for VSE/ESA, Transparent Solutions, Inc, UICVM, University of Regina, University of South Carolina, VM Download Library, VM Update
FAD-H Software
TSO/REXX functions - DSLIST replacement, global variables and dynamic allocation. Also some TSO utilities.
ISPF-L
Mailing list archives, search, and subscription services.
SEC
Includes external Rexx functions, STEMPUSH/STEMPULL, LISTSYM, LISTMEM and SLEEP. MXI system info is also Rexx-callable.
SSC, Inc.
Assembler Rexx functions for dynamic concat, PDS functions, sleep, WTO(R).
Tek-Tips: REXX Technical Help Forum
REXX technical support forum and mutual help system for computer professionals.
TSO-REXX
TSO Rexx discussion list, archives and subscription.