War in the Belt: Belters, Earthers, Marsies. About as hard science as I get.
Aratouk Expanses: Xuvaxi, Ngaksu, Murustan, G'jhekk, Aratouk. Mutually hostile alien slave races fighting over the scraps of the old Aratouk Empire.
Colonials: What it says...
Civilians: Generic commercial and privately owned ships.
Novus Regency: Novus Regency, Privateers, Chukulak, Ikennek, Union. Dashing heroes, implacable foes, and mighty (stylish) warships in spaaaaaaaaaace...
Orion Drive Ships: USS, USSR ships from the secret space wars of the 70s & 80s.
Pocket Empires: Alien Artifacts, Buru, Federation of Man, Imperial Spican Navy and Rabbits. A mostly human universe set so far in the future that Earth has passed into legend.Empires have risen, fallen, risen again in the endless churn of history.
Riitoru Sector: 1/7000 Fleet scale empires. Eltanni, Tusokk, Stravok, Galimek, Badakh.
Voidstriker: Jovians, Martians, Qri, Ryuushi, Mavrideans. From my old boardgame.
The Maelstrom: USASF, LCS, Rukk, Pardosan, Space Roaches, Syndicate, Vespids. Races awaiting a proper background universe.