In short, the Cannae Drive is a theoretical engine that effectively makes use of bouncing microwaves to generate thrust. Some scientists at NASA did some experiments with such a drive and say they generated some small amount of thrust. If this experiment doesn't turn out to be like the superluminal neutrinos of several years ago, further development of this engine could allow us to get to Mars in weeks, rather than months.

I have my doubts about the experiments, and rather believe they will end up being a fluke, but it's nice to imagine being able to explore space more easily.