Here is an rsync command that will synchronize music stored in a Mac to a PC. It will not sync Movies or TV Shows. Just remove the --excludes if you want to sync those things.

rsync -av --force --delete --stats --size-only -e ssh --exclude="ethumbs_vista.db" --exclude="Thumbs.db" --exclude=".DS_Store" --exclude="iTunes\ Library.xml" --exclude="Mobile\ Applications/*" --exclude="Movies/*" --exclude="TV\ Shows/*" ~/Music/iTunes/* /Volumes/itunes

Thanks to MacRumors for the base of this command.