MongoDB (from "humongous") is an open-source document database, and the leading NoSQL database. So the way I think about MongoDB is that if you take MySql, and change the data model from relational to document based, you get a lot of great features: embedded docs for speed, manageability, agile development with schema-less databases, easier horizontal scalability because joins aren’t as important.
Phoenix: How (and Why) we put the SQL back into the NoSQL. Phoenix is an open source project from Salesforce.com that puts a SQL layer on top of HBase, a NoSQL store. This talk will focus on answering two questions: 1) why put a SQL layer on top of a NoSQL store? and 2) how does Phoenix marry the SQL paradigm back together with the NoSQL world? Salesforce.com uses relational database technology extensively, so a big part of the ?why? for us is to provide developers with a familiar API
NoSQL. Next Generation Databases mostly addressing some of the points: being non-relational, distributed, open-source and horizontally scalable. Wide Column Store: Hadoop / HBase, Cassandra, Hypertable, Document Store: MongoDB, Elasticsearch