Beyond Compare - Beyond Compare allows you to compare files and folders.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
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.
DiffMerge - DiffMerge is a graphical file comparison program for Windows, Mac OS X and Unix, published by...
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!