Here is an amusing graphical representation of twist endings, plays in this case. Across the top of the graphic are various story ending types, such as deus ex machina, or story elements, such as a MacGuffin. Across the left side are various genres. The title is "Harvet Ismuth's 42 Essential 3rd Act Twists." This was produced by Internet cartoonist Dresden Codak, a pseudonym for Aaron Diaz (which could be confused with the Latin singer/actor of the same name). Codak also has a one off Caveman Science Fiction cartoon.

Bonus: rhetorical piece about the future of traditional book publishing, on the Galleycat blog of Media Bistro.