Ok, i'm paranoid and I did the following to store the data of OS X's AddressBook on an encrypted DMG volume. Using this method I know all data in my addressbook is unencrypted and available only when I want it to be unencrypted (that is, only when I mount the encrypted DMG volume).
This is nothing great or difficult, is actually pretty dumb, but I thought perhaps someone out there will also find it useful:
1.I assume you already have your DMG encrypted volume or TrueCrypt image or whatever you use created; let's say you mount it at /Volumes/encdisk
2.AddressBook data is stored in ~/library/ApplicationSupport/AddressBook
3.Move everything in ~/library/ApplicationSupport/AddressBook to /Volumes/encdisk/AddressBook
4.rm -fr ~/library/ApplicationSupport/AddressBook
5.ln -s /Volumes/encdisk/AddressBook/ AddressBook
and that's it :)
If your encrypted DMG/TrueCrypt volume is not mounted and you launch AddressBook,, it will of course start executing and will then terminate immediately, which is great! :)
DISCLAIMER: Do this at your own risk; I cannot be held responsible if following this instructions destroys all your data.