Starting with the "Two People Working Together" working together one can check what films three or more actors share in common. For instance, here is a search for titles With Moe Howard And Curly Howard And Larry Fine:
http://www.imdb.com/search/title?role...
One can do something similar for films. For instance, these are the people associated with the "Lord of the Rings" trilogy:
http://www.imdb.com/search/name?roles...