Thanks to one of Bush's brilliant ideas, NASA's budget is now mostly wasted in M2M (the human Mission to Mars) and the rest on the shuttle and ISS. A recent NPR interview put the orginisation further in question. Michael Griffin, director of NASA, doubted whether we would not all be better off under global warming and therefore should not prioritise its abatement.
With regards to the manned Space programme, NASA has recently experienced an astronaut bizarre love triangle and now allegations of drunken flight and systems sabotage. If NASA is to exist, which I believe it no longer should, its beneficial role should be to fund Earth Science, Astronomy, Aerospace Engineering, and general technology research in the public interest.
The Mars Rover and the Galileo and Cassini missions are examples of the incredible benefits that can come from a serious scientifically driven Space agency. The scientific value for those programmes has vastly exceeded the costs because they had the right idea: robotic exploration of outer space. Humans were not designed to live in space and so far the cost of such adventures is no were close to the benefits. Let human space exploration take place commercially as Richard Branson and Burt Rutan are demonstrating. Let scientists do their jobs correctly, and stop distorting their mission and their budgets with a child's fantasy. If children want to go into space, let them finance it themselves.