I find the classification of NoSQL databases useful, if I am going to use a NoSQL db anytime in future I am going to look at this table.

Also I found this website which gives a vast list of NoSQL databases

http://nosql-database.org/>NoSQL Pioneers Are Driving the Web's Manifest Destiny Twitter has scaled back its plans to store billions of tweets using Cassandra, a non-relational database project that Facebook created and open sourced. Friday night, Twitter said that it will still use Cassandra in a new real-time analytics project it is building, but the decision to move away from plans to migrate tweets from its current MySQL database to Cassandra is seen by some as a blow to startups and open-source projects that are attempti … Read More via GigaOM