I just signed up for this service that allows postcards and letters to be exchanged with people all over the world.
This is how it works:
1. Register here, with your name, address, and interests.
2. Request to send a postcard, you will be emailed an address.
3. Pick out a postcard, and write a message along with your assigned sending id.
4. Stamp and mail it.
5. Once the postcard arrives to its destination, you are next in line to receive one!
I just received my first assignment, Bianca in the Netherlands.
photo sources: 1, 2, 3, 4, 5