Doc List writes about one of my favorite activities on his blog, Circle of Questions. I added a few comments there as well.

Esther and I describe the activity in Agile Retrospectives: Making Good Teams Great! We knew when we wrote the description that it would be a difficult activity for people to visualize in action, and we did our best. Subsequently, much to our delight, a number of folks have chosen to experiment with Circle of Questions as their practice activity in our 2-day "Leading Agile Retrospectives" workshops. They take a risk, follow the process, and, voilà, every time it has paid dividends--giving everyone in the workshop a surprising (in a good way) experience.

Doc has begun cataloging Facilitation Patterns and Anti-Patterns as blog posts. He's creating a resource for retrospective leaders and those who facilitate other team meetings, too. Check it out.