Write 'I WOULDN'T LET YOUR WIFE SEE THIS IF I WERE YOU. IF YOU WANT TO MAKE SURE SHE DOESN'T, $200 A MONTH TO MY ACCOUNT. LOVE JULIE' on the front.
and post them through people's letterboxes.
(rnuk http://flickr.com/rnuk, Sun 17 May 2009, 16:27, archived)