For multi-theme sites, Bootswitch allows a site to configure the Bootswatch theme based on a method set in the initializer file.
Customizable bootstrap is designed to get you up and running with a customizable version of boostrap using SASS.
BootstrapLeather is a collection of view helpers and scaffold generators that makes it easier to create apps using Twitter Bootstrap
Like its ancestor Kaminari, BootstrapPager is a Scope & Engine based, clean, powerful, agnostic, customizable and sophisticated paginator for Rails 3+. Now with more shiny, including infinite paging, bootstrap integration, and the ability to use it within an engine.
Private person is an active record extension gem that allows a model to be given privacy settings over arbitrary models and polymorphic relations, putting users' accounts in control of their own privacy policies.
For organizations that want to market a gem in style, Museum uses APIs to provide you with an ever-fresh marketing site for your gems.
Tokenizes strings for use in social applications.
Allows a model of your choosing (such as users) to subscribe to a plan, which enables features.
FriendlyId Extension to allow method scopes, in addition to column and relationship scopes.
Rails 4 & 5 Engine providing private and public messaging for any object, such as Users or Groups
Rails 5 Engine to give users their own calendars of events.
Works cited allows you to add a list of the works cited in ActiveRecord objects, to be formatted by a helper that can be added to relevant pages to format the citations like a bibliography.
Cookbook allows you to associate instructions with components in a cross referenced way. Good for cooking recipes or an instruction manual for DIY projects.