Examdiff Pro - It is a simple yet powerful tool that is being used by the professional programmer and developers for the purpose of visual comparison.
Beyond Compare - Beyond Compare allows you to compare files and folders.
Listium - Share your lists
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Airstory - Airstory is a writing tool that enables bloggers, writers, students and subject matter experts to write better.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.