Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Beyond Compare - Beyond Compare allows you to compare files and folders.
Devart Code Compare - Code Compare is an advanced file and folder comparison tool. Its intuitive interface allows you to merge differing files and folders fast and easily! And it's FREE!
Diff Checker - Diff Checker is a free online diff tool that quickly and easily gives you the text differences...
Araxis Merge - Home of the award-winning Araxis Merge two and three-way file comparison (diff) and merging application, Araxis Find Duplicate Files, Araxis Replace In Files, and the Araxis Ketura issue tracking, project scheduling and time tracking application.