The benefits of having a Mac is its support for the subscription-based .Mac services, of which synchronization between computers is one of its features. Whilst there are tools available on Linux and other *nix-based systems that allows you to synchronize subdirectories across networks, there is nothing like Unison.
Unison is a file-synchronization tool for Unix and Windows. It allows two replicas of a collection of files and directories to be stored on different hosts (or different disks on the same host), modified separately, and then brought up to date by propagating the changes in each replica to the other.
Check out this new discovery that I have made and see if it is useful for you. I know it is for me since I have several machines running on Mac OS X and Linux.