A few months ago I wrote a python script based on unison for synchronizing the iTunes libraries between my computer and Leslie’s. Although you can’t actually merge changes from both libraries, you can push or pull updates, which works well when one computer is a “master” where changes are made and the other is a “slave” where music is usually just played, but the library isn’t added to. You are able to manually push updates from the slave to the master if you like.
Anyway, I finally got around to commenting it a bit and I present it here for download in case others might find it useful: itunes_sync_0.1.tar.gz
I run it from a cron script hourly right now, which is maybe a bit excessive, but it’s all on the local network, so who cares? A better way of doing things would be to only sync when changes have been made, but I haven’t had time to fancy things up like that yet. I run the script only on OS X boxes, but I’m sure if you’re enterprising enough to get unison running on a windows machine it would work fine there too.