It's a basic principle of relativity (both special and general) that if you measure speed locally the fastest speed you can travel is the speed of light. My favourite way to explain this is that it's a consequence of the geometry of spacetime. In fact I've just answered a question on this: Special Relativity Second Postulate
In special relativity the local invariance of the speed of light means there is absolutely no way to travel faster than light, however in general relativity this limitation no longer exists globally. It still isn't possible to travel faster than light relative to spacetime, but in GR spacetime itself can stretch and carry matter along with it, and the net effect is that FTL travel is possible - though physically unlikely.
The most commonly quoted example of this is the Alcubierre drive, varients of which crop up regularly in Science Fiction. Another is the wormhole, though the physics of wormholes are far subtler than (most) SciFi books think.
As a simple example of FTL motion, you probably know the universe is expanding and the recession speed of distant galaxies is (roughly) proportional to their distance. This means that if a galaxy is distant enough it must be moving faster than the speed of light relative to us. Note however that he distant galaxy isn't moving away from us in the sense that a bullet moves away from you when you fire a gun. Instead the spacetime in between us and the distant galaxy is expanding.
You'll probably find the Wikipedia article on faster than light travel an interesting read.