<p>I really like <strong>Araxis</strong> Merge for a graphical DIFF program for the PC. I have no idea what's available for <strong>linux</strong>, though.  We're running SUSE linux on our z800 mainframe.
I'd be most grateful if I could get a few pointers to what programs everyone else likes.</p>

I know of two graphical diff programs:
Meld
and
KDiff3
. I haven't used KDiff3, but Meld works well for me.
It seems that both are in the standard package repositories for openSUSE 11.0