AstroSynthesis 2.0 is a program that lets you create 3D star system maps.
Maps can include randomly-generated features alongside the ones you place, and they can get quite complex. AstroSynthesis drills down to the level of plotting routes between planets (and calculating the distances for you) and allowing you to animate planetary orbits.
I’m not sure I would ever need this much detail to run a space-based campaign, but it would be fun to play with — and nice to know that if I did need to go deeper, I could. There’s also a free trial, and at the moment this puppy has four 5/5 reviews on RPGNow.
Has anyone tried AstroSynthesis?