ActiveRecord Tableless Models provides a simple mixin for creating models that are not bound to the database. This approach is useful for taking advantage of the features of ActiveRecord such as validation, relationships, etc.

ActiveRecord sharding extension

Client Side Validations for Rails 2.x and 3.x

A Ruby on Rails plugin to add an after_commit callback. This can be used to trigger methods only after the entire transaction is complete.

Deploy features incrementally to your users

Chamber lets you source your Settings from an arbitrary number of YAML files and provides a simple mechanism for overriding settings from the ENV, which is friendly to how Heroku addons work.

A malware/botnet analysis framework written in Ruby.

Stores draft versions of your ActiveRecord models' data in a single table or split up into separate tables. Works with Ruby on Rails and Sinatra.

Quickly get a count estimation for large tables.

FortyFacets lets you easily build explorative search interfaces based on fields of your active_record models.

Functional Reactive Programming with EventSourcing in Ruby

Functional Reactive Programming with EventSourcing in Ruby

I18n date/number parsing/localization

Rails Driver and Adapter for IBM Data Servers: {DB2 on Linux/Unix/Windows, DB2 on zOS, DB2 on i5/OS, Informix (IDS)}

Preload ActiveRecord associations with graphql-batch

An awesome nested set implementation for Active Record

Create and modify your notifications through a simple API.

Integrates with your authentication solution to craft a personalized user notification platform.

A ruby library for working with the Open Archive Initiative Protocol for Metadata Harvesting (OAI-PMH)

If you like the straight forward and effective nature of Strong Parameters and suspect that CanCan might be overkill for your project then you'll love Petergate's easy to use and read action and content based authorizations.