It looks like Boeing will be the main competitor for Space X in the race to see what U.S. company will provide the commercial space flight services that NASA eventually plans to rely on.
Space X has its Dragon capsule, and Boeing is developing a new capsule system, called the CST-100. That capsule would ride into space under the power of an Atlas V rocket, an engineering descendant of the Atlas rockets that carried the first four American astronauts to space half a century ago.