This is fun for the beginning of the year. I always introduce this by flickering the lights and telling them that we are about to travel "intoooo theee fuuuuture!" through writing. This is the introduction:
"You will send communications INTO THE FUTURE in two ways. First, you will fill out the questionnaire below, and then you will write a letter to future-you. Both will be saved and given to future-youÃ¢ï¿½Â¦ the you who will exist ten months from now in June of 20__, just as you are about to complete your ___ grade year. You will seal both in a self-addressed envelope, so the contents of the envelope will remain confidential until you re-open it."
The students fill out the attached questionnaire and then write a letter to their "future-you." Then they seal both in a self-addressed envelope (which also helps provide a quick review of how to write on an envelope). I then save the letters until the end of the year and return them the last week. The students always laugh at how much they've changed in just a year. The future-you letters serve as miniature time-capsules of their personalities. If a student moves away during the year, you can just put a stamp on the envelope and send it to the old address (which will hopefully forward it to the new address).