I have been building game worlds since some time in the 1980s, some organizations have appeared again and again.
FFTC - The Far Flung Trading Company specializes in those frontier areas of the world that other merchant houses aren't interested in.
Way Houses - originally The Brothers of the Way, now the brothers of Wei, this small church builds bothies and hostels for travellers.
The Raven College of Armes - Every game-world needs its honours and titles - The Raven College of Armes has done that since the very first game that I ran.
The Golden Billet - A new organization that has only appeared in a couple of games, so far. It provides 'contracted out' protective services to states and organisations.