International Space Station

The International Space Station (ISS) is a joint project of 6 space agencies: the U.S. National Aeronautics and Space Administration (NASA), Russian Federal Space Agency, Japan Aerospace Exploration Agency (JAXA), Canadian Space Agency (CSA/ASC), Brazilian Space Agency (AEB) and the European Space Agency (ESA, with members United Kingdom, Ireland, Portugal, Austria and Finland chosing not to participate; Greece and Luxembourg joined ESA later [1]).
The space station is located in orbit around the Earth at an altitude of approximately 360 km (220 miles), a type of orbit usually termed low Earth orbit. (The actual height varies over time by several kilometres due to atmospheric drag and reboosts. The station, on average, loses 100 meters of altitude per day.) It orbits Earth at a period of about 92 minutes; by June 2005 it had completed more than 37,500 orbits since launch.
In many ways the ISS represents a merger of previously planned independent space stations, especially Russia's Mir 2, United States' Space Station Freedom and the planned European Columbus, representing a permanent human presence in space: it has been manned with a crew of at least two since November 2, 2000. Each time that the crew is replaced both the old and the new crew as well as one or more visitors are present.
It is serviced primarily by the Space Shuttle, and Soyuz and Progress spacecraft units. It is still being built, but is home to some experimentation already. At present, the station has a capacity for a crew of three. So far, all members of the (permanent) crew have come from the Russian or United States space programs. The ISS has however been visited by many more astronauts, a number of them from other countries (and by two space tourists).