vBulletin flowchart
 

Here's a partial flowchart for the newreply process. Hopefully it helps someone while programming a plugin or two or maybe even inspires them to create a more comprehensive flowchart. I created mine with Lucidchart.

Hooks are denoted by squares. The names of the hooks are inside the squares. Files are denoted by bounding green rectangles. Functions are denoted by bounding brown rectangles. A couple important variables that are inherited and accessible are also listed.