Sync for iTunes is an application that helps you keep all your iTunes media synchronized across multiple devices, external disks, network drives, etc. Sync for iTunes is very easy to set up. You simply drag the folder in which you want to create a copy of your library and the sync is established.
You can create exact copies of your libraries if you want to access them from another Mac. Or, you can choose what type of media to synchronize (Music, Videos, TV Shows, Podcasts, iTunes U, etc.), and even decide how to organize it using tags to specify the file structure.