NASA is doing some neat things with propulsion technology short of a nuclear powered rocket. The Dawn mission will be powered by the second Ion Engine after DS1 validated the technology. The New Horizons Pluto mission will get a speed boost from an Atlas rocket that should get it's speed up around 90,000 mph initially.
A viable nuclear rocket is at least 10 years away and that's only if it gets a final go ahead from a timid (afraid of the enviros) congress.
This would have never had happen under a Kerry administration...
Keep in mind ion engines are fuel efficient, not fast. It took SMART-1, what, a year to hit the moon? The fastest way to get to Pluto before the atmosphere freezes is to go the conventional route.