The United States Moon Mission 2020 official name is NASA Constellation Program and is in place to propose, work and deliver on moon colonization by the year 2020.
The moon base would be build at the south pole of the moon. The purpose of this first manned moon base is further manned exploration of our solar system. Unmanned space craft will perform groundwork first, site reconnaissance, technology risk checks, natural resource assessments and general positioning of the moon base. The first missions will be week long missions for a crew of four. Once the habitat is set up 180 day missions are planned for scientists and astronauts.
It would be the first time since 1972 that NASA would send a man back to the lunar surface. The total program is a JV (joint venture) between the 14 largest space agencies in the world, headed by NASA. "NASA's goal is to enable a sustainable space exploration effort in which participating organizations can achieve individual goals with mutually beneficial results."
At this moment the proposed plans are on hold as the US economy does not allow the extremely high budgets to be spend on the program. But NASA has been seeking private funding in a variety of programs, and with a ten year time frame ahead is able to progress and reach its goals.