I came across this website, Postcrossing, which allows anyone to exchange postcards (paper ones, not electronic) from random places in the world. You sign up (for free), request an address to send a postcard to, send your postcard, and when they receive it, your name goes to the top of the list to get a postcard. You can set up your profile to receive postcards from within your country or only internationally - we went the international route for now.
We requested 5 address - the most you can request when you first start out. We'll be sending postcards to:
Finland
Netherlands
Germany
Lithuania
Latvia
We don't know where we'll be getting postcards from (they don't come from the people you send them to), but I'm sure the kids will be camped out at the mailbox until one comes in.