A lot has been said about human settlements on Mars. However, are there any other options? I'm wondering what other planets/moons/asteroids would be good for settling — where else could humans set up settlements after Mars?
If you define colonization as the capability of forming a self-sustaining society with its own technological base then there are no likely candidates with our current level of technology, even Mars. It's very hard to land on Mars because the atmosphere is thick enough to burn you up but not thick enough to slow you down, provide helpful lift, protect the planet from meteor impacts, or allow movement outside without protective suits. It doesn't have a magnetic field to protect life from harsh radiation, and doesn't have much in the way of easily accessed raw materials. The reason you'd want to put boots on Mars is science - humans would be able to answer a lot of questions that probes cannot. Eventually, with significant technological development, the raw materials Mars provides could be used to create the necessities of life, for now just about everything would need to be sent from earth. That's not a colony, but an outpost.
If you define colonization as humans living somewhere then just about any body in the solar system is a candidate, or no body at all. If the earth has to supply everything then a space station makes more sense than a planetary body as you don't have to mess with a gravity well.
Really once we solve the problems that will allow a self-sustaining colony on mars we would be most of the way to colonies wherever we want provided we can deal with the gravity.