Diff Checker - Diff Checker is a free online diff tool that quickly and easily gives you the text differences...
Beyond Compare - Beyond Compare allows you to compare files and folders.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Text Comparator - Compare text from two distinct sources in order to see if they perfectly match or not each other!
Tkdiff - tkdiff is a graphical diff viewer based on the Tk framework.
xxdiff - XXDiff is the name of a graphical file and directories comparison system.