Ruby on Rails: Core - join
Discussion list for Ruby on Rails core development.
Medium activity, 2547 members

Ruby on Rails: Talk - join
The official mailing list for the Ruby on Rails project. Where Rails users come to seek help, announce projects, and discuss all kind of matters surrounding the framework and the community.
High activity, 15116 members

Ruby on Rails: Security - join
Security annoucements for Ruby on Rails.
Low activity, 1693 members