Constellation Program
As part of President George W. Bush's Vision for Human Space Exploration, the Constellation Program is the umbrella program for all human space exploration.
Near-term goals for the program include finding more cost-effective means to put large loads into orbit, a replacement for the Space shuttle, gaining experience in the long-term effects of human spaceflight via the International Space Station, and returning human beings to the moon. Long-term goals include the establishment of a permanent manned lunar base which will be crewed by 6-month crews (similar to the International Space Statiion), and sending humans to Mars and other solar system bodies.
The near-term goals are being met by the Ares 1-X rocket, which being developed as a heavy-lifting rocket to orbit, the Ares V rocket to send loads to more distant destinations (the Moon, Mars), the Orion Crew Capsule as the vehicle in which humans will explore the solar system, and the Altair Lander to carry humans down to the surface of other worlds.