No SQL Databases

A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Motivations for this approach include simplicity of design, horizontal scaling and finer control over availability.

NoSQL databases are finding significant and growing industry use in big data and real-time web applications. NoSQL systems are also referred to as "Not only SQL" to emphasize that they may in fact allow SQL-like query languages to be used. – Wikipedia

NoSQL Database Types:

The Benefits of NoSQL:

When compared to relational databases, NoSQL databases are more scalable and provide superior performance, and their data model addresses several issues that the relational model is not designed to address:

• Large volumes of structured, semi-structured, and unstructured data

• Agile sprints, quick iteration, and frequent code pushes

• Object-oriented programming that is easy to use and flexible

• Efficient, scale-out architecture instead of expensive, monolithic architecture   

Exclusive list of NO SQL Database: http://nosql-database.org/

 Kristof Kovacs comparison of NoSQL databases (Best facts listed out for architect to choose from)