Not that we weren't public before, but somebody posted a link in the magic cafe.
And to honor that. A free non evil way on:
How To Mess With Fellow Magic Folk
Take a deck of cards, shuffle a face up half into a face down half and then throw in a few double facers and double backers. Then ask a magic friend to sort the deck, so it is in normal condition. Takes a while for him to figure out what is wrong.