acts_as_follower is a Rubygem to allow any model to follow any other model. This is accomplished through a double polymorphic relationship on the Follow model. There is also built in support for blocking/un-blocking follow records. Main uses would be for Users to follow other Users or for Users to follow Books, etc… (Basically, to develop the type of follow system that GitHub has)
Socialization allows any model to Follow and/or Like any other model. This is accomplished through a double polymorphic relationship on the Follow and Like models. But you don't need to know that since all the complexity is hidden from you.
EngineY is an easy to use social network framework and portal implemented in Ruby on Rails that is easy to customize and deploy as your own powerful social media site or other portal type site. Empower users with their own blogs. Enhance collaboration with forums, groups and events. Let your users post Twitter-like status messages. Track all the activity on your site with a live activity stream. Build a custom client to access all of your social data using EngineY's RESTful API. Also includes integration with Facebook Connect to allow users to login with Facebook credentials. Recent additions include support for Themes, and Content Management. For project updates and information, follow the project on Twitter @engineyfw