It seems like there's no big consensus on "Good Mac Chess Software."
I wish there was more chess software that played with a GnuChess engine /and/ on the free chess servers. Maybe there is a strong reason for this not being the case. I should investigate!
Anyway, I have found Fixation, which runs on OS X and connects to FICS (freechess.org) where I am rjbs.
Fixation: http://cknelsen.sasktelwebsite.net/fixation/Fixation_title.html
