M Technology Association United Kingdom and Ireland (MUG-UK& I)
A non-profit educational organisation. Its aims are to further the utilisation, improvement and understanding of Cache and the M Technology language and its dissemination within the UK and Ireland.
http://www.camta.net/

MTRC
has info about the MUMPS (M) computer language. Features include an M Job Opportunities database, the M User Directory, and links about MUMPS.
http://www.mcenter.com/mtrc/index.html

M Info Source
The Mumps, Cache and M grand central. Home of M Web Magazine. Links, programs, and articles.
http://www.geocities.com/SiliconValley/7041/

George James Software
Program development, consulting, training, support services; VC/m web-enabled configuration management system to manage documents and source code across many OSs, and add-in tools for Caché and related M technologies.
http://www.georgejames.com/

Forest Software
A software house specialising in M (Mumps). It was formed in 1983 and can provide systems design, programming and support of M based systems.
http://www.forestsoftware.co.uk/

InterSystems M Technologies
A forum and web site for users of InterSystems tools and M in general
http://mtechnology.intersys.com/

M FAQs
Frequently Asked Questions about M/MUMPS
ftp://rtfm.mit.edu/pub/usenet/comp.lang.mumps/

The Mumps Compiler and MultiDimensional and Hierarchical Toolkit
Compiler and interpreter for Linux, Solaris, Windows. Implements much of most recent Mumps standard. [free]
http://cs.uni.edu/~okane/

M[UMPS] by Example
An online copy of part of a book by the same name
http://www.jacquardsystems.com/Examples/

The oMega Project
Implementation of M-Technology+ for Linux. [Open Source]
http://home.clara.net/finch/

CDE Software Systems Corp
MUMPS programming available for Intersystems DTM-PC and DT-MAX platforms available to the greater Chicago and Milwaukee metro areas.
http://www.cdesystems.com/htm/CDE_Products.htm

M User Group Deutschland
The German MUG (in German, of course)
http://www.mug-d.de/

Real Software Co.
Makes M21, implementation of M language/database for the 21st Century.
http://www.m21.uk.com/

4W Consulting
Consulting company specializing in providing expert Cache and MUMPS, and related technologies, application development as well as systems management services.
http://www.mumpsprogrammer.com/

M Web Magazine: "Welcome"
The web's only (now-defunct) M zine.
http://www.geocities.com/SiliconValley/7041/M/mwm.html

MUMPS
Long, growing article, with links to related topics. [Wikipedia]
http://en.wikipedia.org/wiki/MUMPS

Jumps
Java from MUMPS: framework for automated migration from MUMPS language and runtime, to Java and relational databases (RDBMS); implemented as compiler that compiles MUMPS code into Java.
http://www.mumps-migration.com/