Where does Mac OS X store contacts in my Address Book? Has this changed from Snow Leopard to Lion?
The path is
~/Library/Application Support/AddressBook/ on both Snow Leopard and Lion.
Note that you can't see the Library in your home folder (as it is hidden by default). You can type in
chflags nohidden ~/Library in Terminal to make it appear permanently, or hold down ⌥ Option while in the "Go" menu of Finder.