I know that there's been a lot of discussion on the various faster-than-light drives, but i have a few ideas of my own. First, wormhole expansion, basically using particle accelerators to bombard a proton-sized hole in space until it is large enough for a ship to pass through. to use this mode of travel, a ship would need a space in which to put the actual drive (perhaps 40x20x20), making it so that small ships (dropships, fighters, and corvettes) would not be able to break the light barrier without being housed in a larger ship.
The second is a Halo style 11-dimensional slipspace core, which generates a series of small black holes that rip apart the fabric of space in order to enter the compressed, folded realm of the 11th dimension. This could be a smaller, slightly slower alternative to wormhole expansion that could be used on smaller ships.