A penny for your thoughts
One way to deal with the difficulty some participants have getting a word in edgewise is to give everyone an equal number (for example, four) pennies, one of which they put into a bowl in the middle whenever they speak. When they run out of pennies, they can't speak again until everyone else has run out. (In a small group you don't need pennies; just agree that each person won't speak again until everyone else has.)
An interesting variation on this is to make the pennies represent time -- usually one minute or 30 seconds. The bowl or a hat is passed to a speaker who puts in, for example, two pennies, and a timer is then set for two minutes (or one minute, if each penny is 30 seconds). When the timer goes off, the speaker has to stop talking or put in another penny. People who want to hear from someone can give them one or more pennies, to give them more time. Sometimes a "market" in pennies gets going, with people wheeling and dealing at break time. One participant at a conference took up a collection from the men to get a hatful of pennies to be shared by the women ("Do you call yourself a feminist man? Well, put your money where the hat is!") - an interesting approach to affirmative action!
If you think people might cheat, you can use poker chips or other unusual objects instead of pennies.
From http://co-intelligence.org/P-dialogue.html. Feel free to offer revisions and stories.