Explore MongoDB by Joe Lennon (IBM).
From the summary:
In this article, you will learn about MongoDB, the open source, document-oriented database management system written in C++ that provides features for scaling your databases in a production environment. Discover what benefits document-oriented databases have over traditional relational database management systems (RDBMS). Install MongoDB and start creating databases, collections, and documents. Examine Mongo’s dynamic querying features, which provide key/value store efficiency in a way familiar to RDBMS database administrators and developers.
Great way to get your feet wet with MongoDB!