The controversial EM Drive has been tested in vacuum for the first time, and positive results have been reported:http://www.nasaspaceflight.com/2015/04/ ... -em-drive/
Previous tests weren't done in a vacuum, which meant that convection effects couldn't be ruled out.
The vacuum test however would appear to silence this objection.
The EM Drive is a "propellant-less" thruster. There is no firm consensus on how it seems to be producing thrust, with recent interferometer and speed-of-light measurements even suggesting a "spacetime warp" is being created. However some engineers on the nasaspaceflight.com forums have cautioned that this might be due to imprecise measurements.
Hopefully this will turn out better than "cold fusion"...