If you are a ScrumMaster or Coach or Project Manager or Process Facilitator of any kind, I encourage you to become a master of Retrospectives. I just happened upon this great little set of slides and presentation notes about Retrospectives by a couple of people, Sean Yo and Matthew Campbell, done a couple months ago. Very helpful with some practical information, some great links… I strongly recommend checking it out. My only concern is that they limit the scope of retrospectives too much. I have a list of topics that I think can and should be considered in a retrospective:

Technology / tools
Work space / physical environment
Corporate culture
Corporate standards and policies
Teamwork
Work planning and execution
Skill sets
Interpersonal dynamics
External groups
Personal circumstances and needs
The process you are using

This list comes from a presentation I used to include as part of my Certified ScrumMaster course. (Now, in my course I teach three specific methods of doing retrospectives as part of an in-depth simulation exercise.) Here is a PDF version of the Retrospectives Module.