When going gets tough, I go hacking...
Here are some cool packages that run under Emacs - I can't believe I've done something useful!
Both packages are part of the standard distribution of Emacs and XEmacs.
It is a
Plan for Emacs Rescue,
and a venomous PERil.
Viper Is also a Package for Emacs Rebels.
It runs under GNU Emacs and XEmacs and lets you compare, merge, and patch ASCII files with ease.
You will not want (or need) to look at a diff output ever again!
Both Viper and Ediff have been part of the standard Emacs and XEmacs distributions since mid-90's.
Other Emacs resources.