WADptr - WAD compressor
WADptr is a utility for reducing the size of Doom WAD files. The
"compressed" WADs will still work the same as the originals. The
program works by exploiting the WAD file format to combine repeated
/ redundant material.
The source code is portable and will run on most Unix systems as
well as Microsoft Windows and MS-DOS (DJGPP). The program is Free
Software under the GNU GPL.
Documentation, which includes some technical details of how the tool
works, can be found here.