Created for software developers, this is a two part program that is used to make patches for updating software.
Both the manager and the actual patch-program are easy to use GUI-programs.
Command line switches are not necessary on the user's end but it's available.

PatchIt! compares old files with new files, and picks the difference and includes that in a patch-file, which you distribute together with the actual patch-program.

..so instead of putting the whole new version online which may have a size of 3mb, you make a patch file with this great tool and put a file online which have a size of i.e. 350kb.
..isn't that great!?