Pagan Publishing: 1990-Present
appelcline Though a licensee of Chaosium, Pagan may have been the most notable publisher for Call of Cthulhu in the 90s.
chaosium
Green Knight: 1998-2002
Green Knight inherited Pendragon from Chaosium, but their publication was short-lived.
Issaries: 1998-2006
Issaries inherited the Gloranthan rights from Chaosium, but didn't hold them for long.
Chaosium: 1975-Present
Chaosium originally followed TSR with a war game, White Bear & Red Moon. It introduced the world of Glorantha, which would be better known through RuneQuest.