Postcrossing

Have you heard of Postcrossing.com? It sounds interesting.

What is Postcrossing? It's a project that allows you to send postcards and receive postcards back from random people around the world. That's real postcards, not electronic! How does it work?

Request an address and a Postcard ID. Mail a postcard to that address. Receive a postcard from another postcrosser! Register the Postcard ID you have received then do it all over to receive more postcards!