Different users viewing the same contacts/emails

Is there anyway of having, say, two users sharing the contacts without duplicating the data. i.e I want another user to view my contacts without having to copy all the data across to the second user. It would appear that the only shared info on the help is related to sharing using an .mac account. I do not wish to use the .mac account. Is there another way?

The same principle would apply to emails as well, with a joint email account can both users view the same emails without having to having two copies of the emails stored.