Report is an excellent tool that allows us to visually compare if there are differences between 2 or 3 files or even between directories.
Not only can they be compared, but they can be edited and added to one what the other has. With Report we can compare files in popular version control systems such as CVS, Subversion, Bazaar-ng y Mercurial.
$ sudo aptitude install meld
I suppose it is also available in other distributions, of course.