For MAC users
Ircle and MacIRC: Commonly used IRC clients for the Apple Mac OS
  1. Ircle
  2. Macirc
    Important: Current versions of MacIRC no longer supported per current April 2004 Google cached page
    Macirc but there are details at Macirc
    The actual old MACirc site cannot now be displayed
    Another is:-
  3. Snak
  4. a free client recommended by a MAC using Lightfoot fan (click the graphic)

    I do not have a MAC to experiment on but I did notice that there is an auto-join function (If any MAC user finds out how to use this and could then write a short tutorial,I would be very grateful and would add it to this page)
And there is a useful site
"Help for Macintosh IRC client applications"
Choosing and setting up a client for IRC can be a difficult task (even
on a mac :-). These pages should give you some information ...