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Your address book data is found at ~/Library/Application Support/AddressBook. Just copy that folder over to the same location and you'll be good to go (just make sure address book isn't running).

Edit: Or you could just use Migration Assistant to copy all your user data over.
 
reh said:
Edit: Or you could just use Migration Assistant to copy all your user data over.

This route is highly recommended! I've seen some really messed-up Macs from people attempting the drag-copy migration method.
 
I'm not sure if Panther's Address Book had this (let alone earlier versions), but along with iCal, the Tiger version has a Back Up feature in the File menu. I find this to be extremely useful. :)
 
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