"Unison, for those that don't know it, is a handy
little file system synchronization program that runs on Windows,
Linux, and most versions of Unix. It combines the features of both
a configuration management system and a synchronization program. It
will also do its magic across networks. So, for example, besides
letting my friend do a backup from a dead Windows file system to an
external drive, he could have transferred his files to say one of
my servers.
"Of course, most people don't have a dual-boot operating system
setup. If you're a Windows user and you're looking at never-ending
BSODs (blue screens of death) and you need help, Linux can still
come to you aid."