While it isn't pretty KDiff3 is still a decent diff program. I've mainly only used it when I have to do merges between 2 versions of a project. I used Araxis

While it isn't pretty KDiff3 is still a decent diff program. I've mainly only used it when I have to do merges between 2 versions of a project. I used Araxis Merge at a previous job for a bit and really like it. But back then (2005?) their shortcut keys on Windows were atrocious and could not be customized.