File synchronization tool that allows two replicas of a collection of files. Directories to be stored on different hosts (or different disks on the same host), modified separately, and then brought up to date by propagating the changes in each replica to http://www.cis.upenn.edu/~bcpierce/unison/
Compares and merges 2 or 3 files or directories. The file diff shows changes within each line. For Unix and for Windows. Source available under GPL. http://kdiff3.sourceforge.net
CSDiff : text, HTML, or MSWord file difference analysis tool, for Windows 95/98/NT. HtmlDiff : online CGI program to compare any two text files on the Web. Each free. http://www.componentsoftware.com/
Verify the integrity of files, by using the CRC32 or MD5 checksum calculation algorithms. Checksums may be used for revealing the damaged files or compare two files for identity. [Windows 95/98/Me/NT/2000/XP]. http://www.irnis.net/
"Weak" tkdiff, or "Wayne's" tkdiff, an attempt at a minimal version of John Klassa's tkdiff processor. Tcl/Tk source code. http://sheol.org/throopw/wtkdiff.html