Sending a postcard to friends while you are travelling is a time-honored tradition that is rooted in the desire to share experiences. Today there are other options, like e-mail or the telephone, but there's nothing like an old-fashioned postcard.
The postal-loving people over at Postcrossing have taken postcards one step further. They promote sending postcards to random strangers. It's sort an pen-pal system, powered by the Internet. In just five years, Postcrossing has facilitated more than 4.7 million postcards sent by more than 190,000 members to about 200 countries.
The service is free. Once you join, you put your address into a secure database. When you are ready to send a card, they will give you an address somewhere around the world. At the same time, your address will be given to someone else who will send you a card.
It's an interesting way to teach geography and help international affairs.