“Agile Retrospective: Making Good Teams Great” is a great book. It presents a good approach to organize a retrospective and dozens of small “game” that can be used. Triple Nickels is one of them. It is a brainstorming approach where it is very easy to have everyone express their bought and that encourage everybody to be attentive to what others think.
Here is how the Triple Nickels works : the team sits in a circle. If the team is too big, you make 2 or more circles (4 or 5 persons per circle is good). Each team member writes its ideas about the topic you are brainstorming. After 5 minutes, everybody give its paper to the person on its right. That person will then read the thinking of its colleague and complete or responds. After 5 more minutes, they move again the papers to their right and we continue the process until the papers come back to their original writers.
At this stage, everyone has normally expressed his idea, and everyone has read and reply to the most ideas of the others. You can then debrief with the entire team, with already a better understanding of the topics and of the ideas on the table.
This approach is very useful when you have some very quiet persons in the team and some persons that have tendency to push strongly/quickly their ideas.
This is one of the nice activity (or say game, or workshop) presented in this book. Read this Esther Derby, Diana Larsen book to find out more useful tools. You can also search on the web for free available resources like http://retrospectivewiki.org or http://www.gogamestorm.com