What are good books / site where you can learn the best practices for event driven programming in actionscript (3 obviously).
I've got a big project coming up and, to be honest, my flash is usually a big mess of classes and I don't want the the next one to turn into a ball of hair behemoth.
Colin Moock's Essential Actionscript 3.0 has a good explanation of events.
If you want free online stuff, here are some introductory articles on how AS3 Events work with the Display list:
Using Event Dispatcher is for AS2/Flash MX 2004, but is a decent introduction to the concepts of events, event dispatchers, and event listeners.