'No man is an island...'
Most of us belong to various groups and associations and practioners of Magick - especially in a world that disbelieves in the very existence of their craft! - are no exception, something catered for in the core rules by Affiliation. Little is said there about whom you might be affiliated to or what you gain out of the relationship, so here are five example organisations that Magi might join... if they qualify, if indeed they can even find them!
Use them as presented or as templates for organisations of your own. They are based, albeit loosely in the most part, on societies that have existed, or at least might have done, in the real world, certainly in times when magick is seen as plausible. Each has its own philosphy, and may offer training or other benefits to those who join them. They also, as most organisations do, have their own quirks and traditions, perhaps enemies or at least rivals, as well as resources that may be put at the disposal of the membership.
They are well-thought out, and anyone in search of a magical society or two for a contemporary setting - even if not playing Glimpse the Beyond - could do a lot worse than consider making use of them.