On a daily basis, I use two computers, my iMac at home and the PowerBook I use at work. I ran into a situation where I wanted to sync my info such as contacts, calendars and mail accounts from my work laptop while still being able to sync my iTunes library from my iMac. Unknown to me this is possible without any iTunes hacks or plugins, so here is how it is done.

On the computer you want to sync your info with just check the items you want to sync under the info tab and leave the rest of the tabs unchecked. Hit apply and perform a sync.

Now go connect the iPhone to the other computer you want to sync photos, music, videos, ringtones, and podcasts with. Once the iPhone is recognized check the remaining options you want to sync with this computer. You may receive a message saying this iPhone is connected to another iTunes library and all data will be reset, hit ok. This is exactly what you want it to do. It will overwrite only the iTunes library content and keep the info from the other computer.

Once your sync is done you are all setup to sync your info separately from your library.

I hope this helps you out since it is a hidden feature of iTunes.

-bproctor