I'll end with an unexpected application, which suggests that we need planners to understand other people's plans as well as to create our own. Read chapter 26 of Thinking --- Readings in Cognitive Science, edited by P.N.Johnson-Laird and P.C.Wason. It's in the Psychology library. You'll find more about this in Chapter 10 of Charniak and McDermott (which contains a bit on understanding characters' emotions).
If you're not familiar with scripts and frames, both referred to in this article, you may find the articles Scripts and Frames in the Encyclopaedia of AI (RSL) useful.