From Thingamahoochie Software:
WinMerge is a tool for visual difference display and merging, for both files and directories. It is highly useful for determining what has changed between file versions, and then merging those changes. WinMerge has Unicode support, Flexible syntax coloring editor, Visual SourceSafe integration, and Windows Shell integration. Regexp filtering for filenames and lines. Side-by-side line difference and highlights differences inside lines. A file map shows the overall file differences in a location pane. The user interface is translated into several languages.
What's new in this version:
Version 2.14.0 fixed the bug when shell extension uses unquoted program path.