http://en.wikipedia.org/wiki/KEO
The KEO satellite is a satellite space time capsule which will be launched in the end of year 2007 or 2008 carrying messages from the citizens of present Earth to humanity 50,000 years from now, when the satellite orbiting Earth will return. This project is supported by UNESCO (who voted it Project of the 21st Century), Hutchison Whampoa and the European Space Agency, among other institutions.
Every person is invited to write a message addressed to the future inhabitants —
the deadline is December 31, 2006. Messages can be keyed-in on the web, or sent by postal mail. The organisers encourage everybody to gather messages from children, senior citizens and the illiterate so that every culture and demographic on Earth is represented. The satellite has enough capacity to carry a four-page message from each of the more than six billion inhabitants on the planet. Once the satellite is launched, the messages with personal names removed will be made freely available on the web.
KEO will also carry a diamond that encases a drop of human blood and samples of air, sea water and earth. The DNA of the human genome will be engraved on one of the faces. The satellite will also carry an astronomical clock that shows current rotation rates of several pulsars; photographs of people of all cultures; and "the contemporary Library of Alexandria", an encyclopaedic compendium of current human knowledge.
So, SEND YOUR MESSAGES AWAY!
http://www.keo.org/uk/pages/message.php