Code Compare is a free compare tool designed to compare and merge differing files and folders. Code Compare integrates with all popular source control systems: TFS, SVN, Git, Mercurial, and Perforce. Code Compare is shipped both as a standalone file diff tool and a Visual Studio extension.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Beyond Compare - Beyond Compare allows you to compare files and folders.
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.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Diff Checker - Diff Checker is a free online diff tool that quickly and easily gives you the text differences...
P4Merge - A valuable tool for diagnosing continuous integration bugs, Folder Diff also measures how much code must be resolved in pending merge scenarios. Visually compare two versions using image diff within P4Merge to determine changes made.