MirrorX is a very simple .NET application that copies one subdirectory to another, only making the changes required to turn the target into a copy of the source.

This is different from something like rsync because it's not client/server; it's assumed all the files are accessible through the file system (or UNC).

And it's different from something like Unison in that it doesn't try to keep state or previous versions - it's just a very simple tool useful for mirroring files from one location to another on a LAN.