When Andrew Coulter Enright and Heather Samples got married, they had such a diverse group of guests at their wedding they thought it would be a good idea to map out the relationships among them, to make things easier to understand, and to provide a set of conversation-starters. A brilliant idea, in other words, that should immediately be adopted for all situations where two or three are gathered together.
Here's the map:
You can see a variety of biggified sizes at the Flickr link.