This is a quick, fun activity to divide your group into smaller groups.
Give each person a card or post-it note with the name of a farm animal on it (ie. Cow, Pig, Horse, Sheep, etc). To find the rest of their group, they must make the sound of the animal from their card, and then assemble into groups based on their animal (ie. all the pigs together, all the sheep, etc).
Variations include blindfolding participants, or having different types of sounds (nursery rhymes, etc)