Other than the Moon and Mars, where else should we put human colonies in the solar system?

Most other places would be far less hospitable, and a LOT harder to get to. Jupiter and its water-ice moons are 5 times farther from the Sun than the Earth. I think the Moon and Mars are 'IT' for a good long while. Space stations orbiting Europa and Titan would be the most interesting, especially if unmanned robotic probes turn up something interesting there in the next 50 years or so. But any stations like that would be VERY expensive to set up and operate, and if you think we are having trouble keeping the Space Station alive, distant platforms serving no commercial use would be infinitely harder to justify both economically and scientifically.