visual diff editor

I'm looking for an editor/viewer that can show two files side by side with differences. Any suggestions? There seems to be one embedded in cervisia and I recall something called vdiff that was available on solaris a few years back. -- JDL Non enim propter gloriam, diuicias aut honores pugnamus set propter libertatem solummodo quam Nemo bonus nisi simul cum vita amittit.