Example of has_many :through

gistfile1.rb

class UserProject < ActiveRecord::Base
  belongs_to :user
  belongs_to :project
  belongs_to :creator, :class_name => "User"
  # add whatever else you want here, this is your join model
end

class User < ActiveRecord::Base
  has_many :user_projects
  has_many :projects, :through => :user_projects
end

class Project < ActiveRecord::Base
  has_many :user_projects
  has_many :users, :through => :user_projects
end