Postcrossing is a site that allows users to swap postcards with other users around the world.
Lots of people who had pen pals when they were children got to enjoy the excitement of getting mail from someplace else around the world. It not only taught you about another culture, but sometimes helped you improve a foreign language and meet someone entirely different from yourself.
Postcrossing builds on this concept and lets users receive postcards from virtually anywhere in the world where a user has registered for the site. Postcrossing lets you receive one international postcard for every one you send out. You can request postcards from specific locations or just leave it up to chance for a surprise when you find one in your mailbox.
Simply fill in some basic location information about yourself after you create a Postcrossing account and you can get started. You could make your own custom postcard with a program like Adobe Photoshop Elements or just buy one the traditional way. The main point is to get something that shows off something special about the city you live in or your culture. In order to receive cards, you do have to list your address, which requires a little leap of faith on your part. You don't have to list your name or even your gender if that makes you uncomfortable, however.
Once you receive a postcard you can return to the Postcrossing site and log its information. Postcrossing has a postcard gallery for you to display the cards you've received. You can also track how far your mail has traveled in kilometers from your profile.
If you love receiving mail from all around the world, Postcrossing is a great way to track your mail and document your growing postcard collection.