Peter Gwinn, with contributor Charna Halpern, has written a book of long-form improv structures - Group Improvisation: The Manual of Ensemble Improv Games.

(I don't have a copy of the book yet, but I'm assuming that "ensemble improv games" is a different name for what I would call "long form structures", because I know that's what Peter teaches and has experience with.)

The book details a variety of "group-mind" and team-building improv games.