1. MongoDB (from "humongous") is a scalable, high-performance, open source NoSQL database.

    open-source

  2. Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.

  3. HTTP + JSON document database with Map Reduce views and peer-based replication

  4. PostgreSQL is a powerful, open source object-relational database system.

  5. Microsoft Azure is an open, flexible, enterprise-grade cloud computing platform. Move faster, do more, and save money with IaaS + PaaS. Try for FREE.

  6. A distributed open-source database with a flexible data model for documents, graphs, and key-values.

  7. Amazon DynamoDB is a fast and flexible NoSQL database service for all applications that need consistent, single-digit millisecond latency at any scale. It is a fully managed cloud database and supports both document and key-value store models.