Astronaut Don Petit realized something that never crosses our minds when we pop open our mailboxes everyday: why doesn't the International Space Station have an address? Because it isn't stationary and rotates around the Earth? So he made one up based on his precise ISS module location.
Writing on the NASA Blogs, Petit says that frontier stations such as the McMurdo Base, the Amundsen-Scott South Pole Base in Antarctica and even Navy ships have addresses where people can send mail to, so why not the ISS?
My sleep station, a coffin-sized box, is located in the fifth deck space of Node 2. From an Earth-based perspective, I pop out of my sleep station as if I were coming out of the floor. I am thus situated on the International Space Station (ISS) in Low Earth Orbit (LEO) with an orbital inclination of 51.6 degrees (the angle of our orbit plane to the equator) and an average altitude of 400 kilometers. It occurred to me that my address should be: Node 2, Deck 5, ISS, LEO 51.603. The first three digits of your space zip code would be your orbital inclination and the last two a designator for your particular space station, with ISS being the third in this location (after the Salyut series and Mir). This zip code nomenclature should suffice, at least until there are more than 99 different space stations in orbit.
There you have it, space campers, a proper address to reach astronauts working on the ISS. How you'll get your mail up into space and into Node 2 is your problem, not Petit's.