Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Membase vs Neo4j comparison

Redis (V2.4)

Best used: For rapidly changing data with a foreseeable database size (should fit mostly in memory).

For example: Stock prices. Analytics. Real-time data collection. Real-time communication.

HBase

Best used: If you're in love with BigTable. :) And when you need random, realtime read/write access to your Big Data.

For example: Facebook Messaging Database (more general example coming soon)

For other database's comments, please refer to:

http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis