I'm not in a position to run this by the chat right now, so I might as well put this here for people's thoughts. In one sentence, the SCP is an interplanetary rapid-transit system/handy guide to help humans colonize the solar system and beyond.
The transit system takes the form of specific points in space which, when they encounter a spacecraft with one or more living, conscious human beings inside, the craft is instantly and inertialessly accelerated to close to the speed of light and then flies to a similar point in orbit above another planet.
Each planet in the solar system has two of these points; earth's lead to Venus and Mars, respectively. There are two unusual points; one on Pluto, which leads to points unknown, and one on Mercury, which leads to the outer atmosphere of the sun.
The 'guide' takes the form of huge metal plaques covered with inscriptions, orbiting equidistant between the two transit points on each planet. They are covered with the same message in a variety of modern and ancient languages. The message varies depending on the planet, but each is essentially a detailed summary of the planet's geography, atmosphere and climatological conditions, as well as the coordinates of useful mineral and resource deposits and interesting geological features. They also include descriptions, in upbeat, informal tones, describing a variety of means by which the planets might be terraformed to support human life. Each message ends with a small encouraging statement, growing more enthusiastic the further out you go in the solar system.
There are two additional 'guide' plaques, one near the Mercury-Sun point, the other near the Pluto-??? Point. The first is a simple warning that basically reads 'Caution: sun.' The second reads something along the lines of 'You've come a long way, Humanity. Good luck!'
So yeah. Space-based, weird, but more encouraging and mysterious than dangerous.