Assuming you've already read the Most Important Question of the Day (because jeez, if it's that important shouldn't you already have read it?), you may also be interested in this tidbit I came across while researching our upcoming cover story on "The Future": NASA is building a warp drive -- powered by antimatter, just like the one beloved of Trekkies -- to take us to Mars.
Some antimatter reactions produce blasts of high energy gamma rays. Gamma rays are like X-rays on steroids. They penetrate matter and break apart molecules in cells, so they are not healthy to be around. High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material. The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter-powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy.
The matter/anti-matter engine is just a glint in scientists' eyes at this point, but our occasional partners at How Stuff Works have a great explanation of how it might be realized someday.