Honorary. He should be addressed as "Former President Clinton," just as I hope soon to say "Former President Bush" to a second one.

There is only one President.

Leaving the "Former" off just makes it faster to say.

Grover Cleveland was elected twice, with a guy in between. So he could have been addressed as President Former President Cleveland.

Personally, I think they should all be addressed as "Mister" and the correct term to address the President is "Mister President." When we finally elect a woman I don't think that she'll be addressed as "Mistress President," though -- probably as "Madam President."