Check out these Doodle Pillowcases ($19.95, Convenient Gadgets & Gifts). They allow you to write on your pillow case with washable markers, and then wash the messages in the laundry.
This pillow case would be great in three scenarios:
1. You wake up with a stranger in your bed and need to hightail it out of there. You can scrawl, "Thanks for the memories, lose my number" onto the pillow and they'll get the message when they wake up, naked and confused.
2. You have been nagging your significant other to do something, and they haven't lifted one goddamned finger. Let them know that they REALLY need to stop leaving dirty clothes on the floor by leaving a message right where their fucking face goes.
3. Kids. Kids will love it.