In the old Engines plugin (used before the built-in engines arrived in rails 2.3), controller and helper classes were mixed together. That is, if an engine had a FooController, and your application also had a FooController, you could use the actions in both controllers. In the built-in Engines ...

Attach files (images, videos, pdfs, txts, zips and etc) to a MongoMapper record. You can choose if you to store it on file system or GridFS.

Easy manipulation of sets of ActiveRecord models

mongoid plugins

It is a MongoMapper's plugin to add auto incremented id in MongoMapper's documents.

Moonshado SMS gem

Catalogs music file data and exposes a playlist interface

The base engine for the muck system. Contains common tables, custom for, css and javascript.

This gem contains the rails specific code for dealing with feeds, aggregations and recommendations. It is meant to work with the muck-raker gem.

DB constraints in migrations similiar to ActiveRecord validations. Core classes

Postgresql constraints in migrations similiar to ActiveRecord validations

This gem reads exchange rates from the National Bank of the Republic of Belarus website. It uses it to calculates exchange rates. It is compatible with the money gem

The fastest dependency injection framework

utella is a framework to create and run RoomApps

Oembed Provider Rails 3 Engine

Add Ogone payments functionality to your Rails application

OpenStack Ruby and RoR bindings implemented with ActiveResource - See also http://www.unicloud.it

openvpn_management is a ruby gem for openVPN (server) management interface interaction.

Connect your RAILS app to OTRS/ITSM

Smart fields for your forms, similar to Formtastic or SimpleForm