Is there a mailing list for CA-Clipper users on the
 Usenet/Internet/Bitnet?  Fidonet?  Others?

 Yes.  You can subscribe by sending the message "SUBSCRIBE CLIPPER
 Your-Name-Here" to <LISTSERV@BRUFPB.BITNET>.  Send list
 contributions to <CLIPPER@BRUFPB.BITNET>; administrative requests
 go to <LISTSERV@BRUFPB.BITNET>. Do not ever send administrative
 requests to the list address.

 On Fidonet, check the CLIPPER echo.

 There is also an active CA-Clipper echo on the cozier but
 lesser-known GT Power network.