A readonly ActiveRecord-esque base class that lets you use a hash, a Yaml file or a custom file as the datasource
Ruby persistence framework with entities and repositories
The Official Ruby Object Mapper for MongoDB
A Ruby Object Mapper for Mongo
Ruby ORM for MongoDB (compatible with Rails 3)
Object-Hash Mapping for Redis
Map Redis types directly to Ruby objects
ORM for Redis
Data mapping and persistence toolkit for Ruby
Sequel: The Database Toolkit for Ruby