If you're participating in Paper Garbage/Write Your Friends month, here's an additional way to pass them information:
[H]ere we publish the secrets of the language of stamps. If the stamp stands upright in the upper right corner of the card or envelope, it means: I wish your friendship. Top right, across: Do you love me? Top right, upside down: Don’t write me any more.
And so forth. (Including "You're right about my lady-friend" — right-hand top corner.) There doesn't yet seem to be code for "Inside this package you will find a piece of beautiful coded jewelry, from me to you, for no reason," but we could probably come up with something. [Via]