Wye provides users of ActiveRecord 3.2 with scopes and block methods for contextual execution of database queries on alternative database connections. Wye's patterns are most useful to applications making use of either replicated or federated databases.

Supports MongoDB style sharding and mirroring

ActiveRecord Tableless provides a simple mixin for creating models that are not bound to the database. This approach is mostly useful for capitalizing on the features ActiveRecord::Validation

Provides methods to fetch, cache and utilise historic exchange rates in your app.

Gem for automatic scaffolding by Ermes-x.

Full control over schedules for use with adnX's xTeam software

A Rails model validation, my first gem, just a practice work

Xylem provides a simple way to store and retrieve hierarchical data through ActiveRecord.

http://yalebulldogs.com/

DbCharmer is a Rails plugin (and gem) that could be used to manage AR model connections, implement master/slave query schemes, sharding and other magic features many high-scale applications need.

A Ruby gem for YAML serialization and deserialization of ActiveRecord models with JSON schema generation.

I'll clean your data

Yet another paginator for Ruby on Rails adding pagination and filtering interface to ActiveRecords.

Yet another publish subscribe gem

The goal of this gem is to facilitates the use of Active Record in non Rails projects. The tasks in the db namespace that we use when developing Rails applications are a nice part of our lifes, so this gem tries to glue this in your application too.

YDD is a tool (a fork of yaml_db really) to make it generally easy to use it for things like copying databases from production to staging and the like.

Makes working with weeks more fun

SQL "raw" for Rails projects

Store yinx metadata with activerecord

ROXML is a Ruby library designed to make it easier for Ruby developers to work with XML. Using simple annotations, it enables Ruby classes to be mapped to XML. ROXML takes care of the marshalling and unmarshalling of mapped attributes so that developers can focus on building first-class Ruby classes. As a result, ROXML simplifies the development of RESTful applications, Web Services, and XML-RPC.