There is a few more MP Only or MP capable games that are coming soon:

Naumachia: Space Warfare (coming soon)
Heresy War (coming soon)
Combat Simulation System (coming soon)
Evochron Mercenary (out now)
Jumpgate Evolution (coming soon)
Black Prophecy (coming soon)
Infinity: The Quest for Earth (coming not so soon)
Taikodom (out now/beta)
Vendetta Online (out now)
Miner Wars (coming soon)

There is a few others I am missing but all of these games do have a dedicated area on SSC. And there is a bunch of indie space games in the works and some nice SP games coming as well.