I just got back from the office and synced contacts so it can definitely synch to 2 iTunes, different options to sync. My calendar and contacts are on the office computer so I synced from outlook. I keep music on home computer.
The only thing I had to do was when I first connected to my office computer, I canceled the sync (you can do that using the slider on the phone) to keep my music which unchecked everything in iTunes. Then I went back in and check off the syncs I wanted to happen, hit apply and voila. Good to go.
At home I have the sync to outlook options not checked.
I let it just write over everything because I've always kept everything in my office outlook, but there was an option to check that let it overwrite what was in my address book. I assume if you don't check that option, the home contacts might be kept. There are also differnt folder syncing options? Perhaps keep two folders, work and home and sync them to two different computers?