One thing I make for myself that I am not sure I have ever seen in a published module are relationship webs: just a bunch of pictures of NPCs in the situation (I steal headshots from the internet) with a name and basic description, connected to the other NPCs with various kinds of lines and arrows that give an indication of the relationship. A line with a heart means romantic ties, a line with a lightning bolt means contentious, etc... That way, with a glance I can see who feels what about whom, so when the PCs get involved I can have NPCs respond according to their relationships without having to try and keep all that stuff in my head.