I'm replying both to Eric as well as the list, in hope that this idea
sparks further suggestions...
 
In terms of developing a user-friendly client in the Macintosh world, I
would think that a Hypercard-based application would be the best way to
go. Given that all Macs are shipped with at least a fully functional
Hypercard player (i.e., runtime module), such an application would be
usable by the majority of Mac-equipped Listserv users.
 
As an example of a nicely executed hands-on Hypercard tutorial, I suggest
you ftp anonymously to nnsc.nsf.net and retrieve the file
Internet-Tour4.0.2.sit.hqx, located in the root directory. You need at least
Stuffit 3 to uncompress it, but that's found on sumex-aim.stanford.edu,
in the /info-mac/util directory. (As a side note, you might also want to
take a look at this Hypercard stack, for use as an introduction to the
Internet by your new users).
 
Hope this helps.
 
Juan Courcoul