Meld
- A gnome2 diff, and merge tool for file comparisons. Edit files in place and the differences are updated dynamically. It also integrates with CVS either as an external tool or via the built in browser.
- http://meld.sourceforge.net/

XDiff
- Rudy Wortel's X11/Motif based file comparator and merge tool for IRIX, SUN, Linux and AIX. Free, no source code.
- ftp://ftp.sgi.com/sgi/xdiff/xdiff/index.html

Diffstat
- Makes ASCII histogram from diff output. Download targz source.
- http://dickey.his.com/diffstat/diffstat.html

XXDiff
- Graphical front-end for diff. Open source Linux targz, FAQ, screenshots.
- http://xxdiff.sourceforge.net