neo4j - Meet Neo4j: The graph database platform powering today's mission-critical enterprise applications, including artificial intelligence, fraud detection and recommendations.
ArangoDB - A distributed open-source database with a flexible data model for documents, graphs, and key-values.
Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
GraphDB - What should you know about the GraphDB software? GraphDB is a form of semantic graph database that organizations can use to manage, organize, and store information in the form of smart data... read more.
OrientDB - OrientDB - The World's First Distributed Multi-Model NoSQL Database with a Graph Database Engine.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.