Leopard lets you create groups from other user accounts on your computer. When creating a new account, choose Group as the type of account. Then, name the group and select the users you want to include in it:
Creating a group lets you assign permissions to an item for multiple individual user accounts simultaneously. A group can contain local users and sharing only users. After you have created a group, give that group permission to an item in the item's Get Info window:
Like user accounts, you can Control-click a group name to access its advanced settings:
