Stars Without Number
This game setting makes it easy to create and play within a vast science fiction universe. Highly customizable and popular enough to have inspired a wealth of fan-made resources, Stars Without Number is a great system for your space-faring adventures, whether they be grand space operas or gritty Firefly-esque missions.
Here is a compilation of free online resources to aid in the creation of Stars Without Number games:
And this PDF contains blank character, planet, ship, and faction sheets: