https://github.com/metaskills/grouped_scope http://metaskills.net/2008/09/28/jack-has_many-things/ </p> An old ActiveRecord extension that I just updated to work with ActiveRecord 3.1. GroupedScope provides an easy way to group objects and to allow those groups to share association collections via existing has_many relationships. It also maintains existing existing scopes, association extensions and options defined in your original collection association. Some new things in this release: (1) Very minimal extensions in ActiveRecord (2) Uses ActiveRecord::Relation and Arel internally (3) Now uses Arel/SQL for the group scope vs. a ton of member IDs.