According to this article, NASA is looking for a "space taxi," or more accurately, proposals for a commercial passenger transportation system to space. They plan to use $50 million of economic stimulus funds as "seed money" for this program. Such a system could help fill the gap in astronaut transportation to the ISS between the 2010 retirement of the space shuttle and the 2015 (probably later) availability of the Orion spacecraft and the Ares I launch vehicle (or whatever NASA ends up developing after the Augustine NASA Review Panel makes its recommendations). The current plan is to buy seats on Russian Soyuz spacecraft at $50 million a flight until a US-based system is available.
It would seem that SpaceX has a leg up on this program with its private Dragon spacecraft program, currently in development (with some NASA funding) to carry cargo to the ISS. Dragon was designed from the start to be extended to carrying passengers, with the addition of a few critical parts like seats and a crew escape system. But the escape system is a big ticket item (estimated at $300 million to develop), so $50 million won't go very far, assuming SpaceX wins the competetive bid. But as Elon Musk says, at least it's a step in the right direction, calling people's attention to the post-shuttle gap.
Of course it's not likely a real "space taxi" will look like my picture. This is an Orbiter add-on called "Space Taxi 2" by "lumpiluk," inspired by a German movie.