Typically, a group in Second Life is an organization which consists of at least two Residents. Using the 'group' function in Second Life, groups can establish themselves formally. Such groups have access to a moderator group-chat, and at least two (and up to ten) assignable roles with different abilities and are able to own land/items. Members in special roles can send notices to all group-members and can create proposals where others are able to vote. Any Resident can be a member of up to 42 different groups.
Below is a list of Second Life groups and coalitions - some formal and joinable, some not.