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.

Adds new features to Arel

Deploy features incrementally to your users

A malware/botnet analysis framework written in Ruby.

Quickly get a count estimation for large tables.

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

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)}

never let an unscoped Model.all accidentally leak data to an unintended audience.

Extend Ruby on Rails ActiveRecord with Neo4j nodes. Keep RDBMS and utilize the power of Neo4j queries. Originally by @elado.

An awesome nested set implementation for Active Record

Write-through and Read-through Cacheing for ActiveRecord

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)

use pagy for cursor-based pagination with rails

Extends Paperclip with Dropbox storage.

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.