I have four different sci-fi universes going right now. Two different cyberpunk ones and two different space-opera ones (minus the aliens).
The latest one I've been developing is the space-opera-ish one for the computer game I'm planning and writing at the moment. It's a multi-solar-system one grounded in reality (the Sol system has been colonized and humanity has since expanded outward, Earth is still the cradle and center of human civilization, etc.). There is no traditional faster-than-light travel (inter-system flight is done through jump gates, intra-system flight often takes several days), space ship maneuverability is constrained by realistic physics, and most space flight is commercial, with very few personal space ships.
Within the universe, a future, expanded UN is the governing political body of humanity, with local branches governing each planet, space station and asteroid colony in known space. There are factions that oppose the UN government, to varying degrees of vocality and radicalism, but most aren't found in the core systems in any kind of force, preferring to operate out on the edges of UN-controlled space where their influence is less profound and the people are more likely to be sympathetic to dissension.
There's a whole bunch more I could get into, but that would be going into game-relevant information, which may or may not be of interest (and may contain potential spoilers) to some people here.
_________________
It takes a village to raise an idiot, but it only takes one idiot to raze a village.