In a dozen juvenile novels (that's novels for young people, not novels written when he was young), Robert Heinlein laid out a manifesto for the exploration and colonisation of the solar system. Arthur C. Clarke supposedly remarked that the Moon landings justified all science fiction to that date. Everyone expected colonies on Mars, generation ships etc. by 1985. But, for various reasons, the exploration of space has been left to unmanned vehicles, while human activity has stopped at the low earth orbit of the International Space Station.
(Speaking of unmanned vehicles, there is some blogger buzz – but no confirmation from NASA – that Voyager 1 has in fact finally left the solar system).
Reading NASA's press releases sometimes it does indeed seem that they just want to discover the effects of weightlessness on little tiny screws:
(Look! A legitimate Simpsons clip on YouTube!)
It may quiet the shades of Heinlein, Clarke and Asimov to learn that NASA is looking into the possibility of building a Gateway to the Moon at L-2 (one of the five Lagrangian points where the gravity of the Earth and the gravity of the Moon cancel each other out). And, as if that is not enough, they are also looking at the possibility of mining in the asteroid belt. All we need now is Delos D. Harriman telling us we have got to be believers.