Good icebreakers for a group of 10 to 30 people are "Two Truths and a Lie" and "Great Wind Blows." "Great Wind Blows" also works for groups of 30 or more, as does "Who Am I?"
To play "Two Truths and Lie," gather the participants in a circle. One at a time, a participant shares three statements with the group. Two are truths about himself and one is a lie. The group must guess which of the statements is the lie.
Set up one less chair than the number of participants to play "Great Wind Blows." The one person who does not have a chair starts in the middle of the circle and makes a statement that describes something about himself, for example, "Great wind blows for everyone who loves chocolate." Anyone who loves chocolate must get out of their seat and find a new seat at least two seats away from where they started. Similar to musical chairs, whoever is left without a seat becomes the caller in the middle of the circle for the next statement.
"Who Am I" requires the facilitator to create name tags for all participants ahead of time. The name tags should have names of famous people or characters that everyone will be familiar with, for example, Superman, Indiana Jones, Britney Spears or Mickey Mouse. As participants arrive, place a name tag on their upper back. The participants walk around and talk to other people to try and figure out who they are by asking those they converse with "yes" or "no" questions only. For example, "Am I a female?" or "Am I a Superhero?"