Check out this recent XKCD.
It's a series of diagrams of character relationships for different movies (including Lord of the Rings). You know, who is together at what time, paths crossing and diverging, etc.
It would be an interesting exercise (though I'm not going to attempt it) to do this for the Malazan Book of the Fallen or A Song of Ice and Fire. You know, some multivolume work that's really, really complicated.
If there's anything quite like this out there for those, post a link in the comments!