As pointed out by Cal Evans on the Zend Developer Zone, there's a new look at Observers and Dispatchers over on Peter Goodman's blog.

Maybe you've used a framework that uses Observers and Dispatchers, or you've heard of them but don't know how they work. Well, I'm going to explain them and tell you why they're so useful.

He starts with a table defining the parts of this dynamic duo before jumping into the code examples and explainations. His first example is just a basic use of the pattern, while the second involves using a MySQL table for the notification events.