Firstly, to those of us talking about FTL travel. The Alcubierre drive was an interest of mine a bit back, and, although it requires the manipulation of negative energy, it's still interesting to look at.
http://en.wikipedia.org/wiki/Alcubierre_drive
Light has no mass, and yet it's constricted to travel at lightspeed. And, so far as conservation of energy and relativity are concerned, we're fairly close to bodies of light. e=mc^2, so mass can be converted to energy (the most prominent example of this being antimatter, where an electron and positron can annihilate one another, forming a pair of what tend to be gamma-ray photons).
The problem with exceeding the speed of light is that it's an inverse relationship, as it gets higher, or a hyperbola on a graph. As your speed increases to near-c speeds, a certain portion of your acceleration is converted to mass (of course, that's a simplified explanation, so don't go attacking it for the various.. things I've left out).
As an arbitrary example, acceleration from .9 c to .99 c, for a single atom, might require a few million newtons. (Again, arbitrary. I'm tired, and doing the math right now is beyond me). Acceleration from .99 c to .999c might require the exact same amount of energy, despite the fact that we're accelerating about a tenth as much.
You can't actually *reach* the speed of light if you have mass, as an infinite amount of energy is required to do so. The speed of light is only there as the 'universal speed limit', something we believe nothing can exceed. (although wormholes and Alcubierre drives could *effectively* exceed light, in that they would manipulate the fabric of the universe around them to achieve this travel, the atoms of the spaceship would still not be able to reach, or exceed lightspeed.)
Besides, time dilation is plenty good, if you want to send out colonies. I see the most viable plan for long-term colonisation the construction of massive colony ships, with equally massive engines, reaching relatavistic speeds to make time pass more slowly for the inhabitants inside. Of course, there are a HOST of problems that go along with that one, but it doesn't really require any new discoveries.
After all, the universe has a long time left to go. Even if we put the maximum speed of humanity at .1 c, we could still slowly colonize the galaxy, and eventually the majority of the known universe.