With estimates that top 100 billion dollars once all the repairs, expansions and updates are completed, the International Space Station is a pricey undertaking. Begun in 1998, it's a jointly operated orbiting laboratory and observation post that will also function as a base for other human forays into space.
Currently being assembled in low orbit, the completion date was originally set for 2006 but may now be delayed to 2010 and beyond. An estimated 80 shuttle trips will be necessary to complete the project. With the discovery of water on the moon and Mars, new interest and excitement in space colonization (at least as far as a base on the moon is concerned) may help free up enough money to get the project completed soon [source: Oberg].