Our mailing list is <ctwm@ctwm.org>. This serves as both a development list where improvements to CTWM are discussed, and a user/support list where you can get help with problems you run across or discuss and compare your CTWM usage with other users. This is generally a low traffic list, but there are plenty of people on it, so you can count on getting responses!
To subscribe, send an email to minimalist@ctwm.org with the subject line "subscribe ctwm".
There are several archives of the list on the web:
In previous years, the CTWM list has lived at several other places, which are now defunct. Archive links are collected here for posterity.
Prior to 2014, the list was hosted by Richard at free.lp.se. The gmane.org link above includes those archives, which are also available at https://www.mail-archive.com/ctwm@free.lp.se/.
Before 2003, the list was hosted by Claude at listes.epfl.ch. An archive is available at https://www.mail-archive.com/ctwm@listes.epfl.ch/.