There is one kind of plot device you're forgetting:
Hyperspace
Hyperspace is another plane, located outside normal space, where you can open a wormhole or jumpgate and enter hyperspace, go a few AUs, then re-enter normal space and you'll have gone the equivalent of 10 light years. It figures prominently in the Babylon 5 universe, where hyperspace can drift your ship away from navigation beacons and be lost forever, or where alien races can hide. In Babylon 5 it's done through jump gates, massive devices which open the entrance to hyperspace, or by ships powerful enough to create their own jump points. The Shadows' vessels are capable of fading in and out of hyperspace. Star Wars uses this as well. Star Trek has subspace which is a similar concept. In the Mechwarrior series, ships use hyperspace to travel quickly. The game Starlancer uses this as well.