A DataMapper adapter for the Google App Engine Datastore.
Currently this is pretty basic. There's no support for Parent entities, transactions, Blobs, or Links, for example. Any query supported by the Datastore should work. That means the like, regexp, and not operators are not supported. Or is only supported for fetching several entities by the Key.
DataMapper likes to lazily load properties. The Datastore always sets and returns all properties on an entity. If you have lazily loaded properties strange things will happen (like properties potentially disappearing).