1)   WinMerge 2.4.6
WinMerge is a tool for visual difference display and merging, for both files and directories. Unicode support. Flexible syntax coloring editor. Windows Shell integration. Regexp filtering. Side-by-side line diff. Highlights differences inside lines.
diff, merge, text files, differencing, syncronize,

 2)   DiffDog Standard Edition 2005
Altova DiffDog 2005 Standard Edition is the dedicated differencing utility for developers and power users. This easy, powerful synchronization tool quickly compares files and folders then highlights differences and merges content via an elegant GUI.
diff, differencing, diff files, diff xml, file comparison, file differencing, diff utility, merge files, text comparison, xml differencing,

 3)   DiffDog Professional Edition 2008
Altova DiffDog 2008 is the developer’s dedicated differencing utility. This unique XML-aware synchronization tool quickly compares files and directories then highlights differences and merges content via its straightforward visual interface.
diff, diff/merge, differencing, diff files, diff source code, file comparison, file differencing, diff utility, merge files, text comparison,

 4)   Visual Patch 1.0.0.3
Provides software developers with a comprehensive solution for creating secure full-history software update patches. Visually indicates the differences among product releases and automatically builds only those changes into a single-file patch.
patch, patching, update, updating, update maker, rtpatch, binary patch, make updates, history patch, history patching,