Kinto : Kinto is a lightweight JSON storage service with synchronisation and sharing abilities.
CouchDB : Apache CouchDB™ is a database
that uses JSON for documents,
JavaScript for MapReduce indexes,
and regular HTTP for its API
RethinkDB : RethinkDB is the first open-source, scalable JSON database built from the ground up for the realtime web. It inverts the traditional database architec...
OpenKeyval : OpenKeyval is a completely open key-value data store, exposed as a drop-dead simple web service. The goal is to make this a very easy way to persist d...
A Lawnchair is sorta like a couch except smaller and outside. Perfect for HTML5 mobile apps that need a lightweight, adaptive, simple and elegant persistence solution.