The postcrossing official forum where you can chat with other members of this project.
Postcrossing gallery for posting pictures of the received postcards.
Postcrossing twitter for quick updates on the project.
Postcrossing Facebook group for the users of this big social network.
An orkut community around postcrossing.
Allows you to track your Euro bills around the world.
This project is making 1000 journals travel around the world.
A French project that allows it's users to exchange surprises.
The Letter Writers Alliance is dedicated to preserving handwritten letters - all sorts of goodies related with that!
The postsecret project allows people to reveal their secrets using postcards.