Another gorgeously science-fictional concept: that of the constantly shifting gravitational corridors in the solar system that will allow for the rapid transit of spacecraft around the Sun:
Scientists in the U.S. and Germany are attempting to map the corridors to allow them to be used by spacecraft exploring the solar system. One of the researchers, Shane D. Ross from the Virginia Polytechnic Institute in the U.S. described the system as a series of low energy corridors that wind between planets and moons. Once a spacecraft entered a corridor it would “fall” along the tube, much as an object falls to Earth.
If and when there is a substantial demand for intra-system space traffic these channels in space will become like the shipping lanes of the oceans of Earth.
[from Physorg][image from TheAlieness GiselaGiardino²³ on flickr]