slackscan is a simple utility that identifies unused space within the filesystem. In particular this tool is just a filesystem scanner that looks for slack space (unused space associated to a file).
The framework of this scanner can be extended to do much cooler things, get creative and hack it up.
e2fsprogs - http://e2fsprogs.sourceforge.net/
Simply run make to build.
mattdavis9@gmail.com (enferex)