Prodigal Empires is my science fiction background. It is based upon my love of such relatively low tech, human based science fiction backgrounds as the Alien franchise, Stargrunt, Rogue Trooper and Judge Dredd.
The basic concept is that a dying Earth was abandoned by humanity in waves – planets first settled by generation ship colonists and then by subsequent waves of colonists who came later, from different backgrounds in faster-than-light craft.
Currently there is general background on Prodigal Empires (especially the multiple colony Archane System) and the D6 Space RPG campaign currently on hiatus
There are also two wargames;
The tounge in cheek Full Thrust starship battle campaign
And the multiple colony scrap on the moon (and island of Nueva Esperanza) which combines table top battles with play-by email strategy.