KEO is a satellite built to return to Earth 50 000 years from today. It shall bring back to our far away descendants every message that each and every one of us is invited to put on board.
This means that you can send email to them and after 50 000 years the satellite will come back here (if there is any life) and the "new" people will read your message!
You can write your messages in this form:
http://www.keo.org/uk/pages/message.php
Rock it on!