Magento uses a fantastic event hooking system, following the Observer Design Pattern, allowing additional functionality to be plugged in and out without modifying the core code.

This list of events is automagically extracted directly from the Magento codebase. It's pretty unlikely that anything was missed but if you do notice something, get in touch. 

Nick Jones is a Magento Certified Developer and Technical Director of Meanbee, based in Bath, UK. Read his articles and find out how to get in touch.