I recently installed a new harddrive on my Macbook. Before proceeding, I made a backup of my entire drive using SuperDuper. I wanted a fresh install, so instead of just dumping the old disk image on the new drive, I installed Leopard and started selectively copying what I needed.
Everything went well until I wanted my Address Book back. Unfortunately, all advice concerning backing up Address Book is along the lines of „Start Address Book and select ‚Back up‘ from the ‚File‘ menu“, but no one tells you where Address Book actually saves the addresses. The easiest way to find out turned out to be using Instruments to monitor what files Address Book opened on startup.
To make a long story short: to transfer entries from one computer to another, just copy the Folder:
/Users/.../Library/Application Support/AddressBook
You may not be able to overwrite some files, because they are in use by other programmes (in my case the culprit was Safari). You can figure out which programme currently has files open using fuser
in the Terminal.