If you are planning to develop a new social networking web site using Ruby on Rails, you should take a look at these extensions.

Community Engine

  • Type: Plugin
  • License: MIT
  • Real world usage: Curbly, Uncooped
  • Features: Authentication, user profiles, user search, user blogs, forums, photo gallery, clippings, tagging, commenting, comment notifications by email, activity feeds, etc.

Lovd by Less

  • Type: Rails Application
  • License: MIT
  • Real world usage: ImitateLife, Jamzee
  • Features: Authentication, admin panel, user profiles, follow a user, user-to-user messaging, user blogs, user search, photo gallery, commenting, activity feeds, Flickr integration, YouTube integration, etc.

Insoshi

  • Type: Rails Application
  • License: GNU AGPL
  • Real world usage: Insoshi Developer Site
  • Features: Authentication, admin panel, user profiles, user-to-user messaging, user blogs, user search, forums, photo gallery, commenting, activity feeds, etc.