Mongoid is an ODM (Object Document Mapper) Framework for MongoDB, written in Ruby.

A pure-Ruby driver for connecting to, querying, and manipulating MongoDB databases. Officially developed and supported by MongoDB, with love for the Ruby community.

MongoMapper is a Object-Document Mapper for Ruby and Rails

Persistence layer for Ruby objects

Mongomatic is a modular Ruby object mapper for Mongo

Object Model for MongoDB

Library to interact with databases, not tied to rails, and not tied to active record pattern