Just sent 5 postcards out to people from PostCrossing.com. When you sign up, you retrieve up to 5 addresses to whom you are to send a postcard/letter to. When they receive it, they enter in the postcard ID, and then qualifies you to receive a postcard from someone else.
So if you live in Italy, the Netherlands, Germany, Finland or California - you may just end up getting a card from me!!
[Provided you also signed up on PostCrossing.com. You have, haven’t you??]