There are a lot of nice things about the iTunes (and Apple in general) ecosystem. As long as the way you want to work is the same as the way Apple built it, things are generally hunky-dory, easy to use, and reliable. Stray away from Apple orthodoxy, though, and things can get ugly really fast. A prime example of this is trying to keep one iPod/iPad/iPhone in sync with an iTunes library through multiple computers.
Between Apple and the recording industry's piracy paranoia, they have contrived to make it very difficult to plug a device into multiple computers without having everything on the handheld device wiped out. However, thanks to the amazing cloud storage solution known as Dropbox, there is an answer. The beauty of Dropbox is that once you create an account, you can install a local application that automatically syncs selected folders to the cloud. Linking multiple computers to the same account will keep copies of all of the desired files and folders in sync on all of those machines automatically and seamlessly.
Syncing the media files is pretty straightforward, but iTunes keeps track of portable devices and sync status through its library database, an XML file that is easily corrupted. Plugging the iPod into a computer with a different library file will prompt iTunes to wipe all of the data from the device. Getting around this requires keeping the library file in sync through Dropbox as well, but this is not quite as simple as it sounds. Because iTunes expects the library to be in a very specific location, you have to delve into the OS X terminal to create a symbolic link that fools iTunes into thinking the library is still where it was originally created. This technique apparently works reliably for the most part, as long as you don't open the library from multiple computers simultaneously, which will break everything. Head over to the source link to get the detailed instructions.