Hi, MongoDB is a document-oriented database, opensource. Check out the videos.

Introduction to MongoDB – Part I from Eric Berry on Vimeo.

Introduction to MongoDB – Part II, Ruby from Eric Berry on Vimeo.

Introduction to MongoDB – Part III, MongoMapper & Rails from Eric Berry on Vimeo.

Some other video links: http://www.leadit.us/hands-on-tech/MongoDB-High-Performance-SQL-Free-Database
http://ia301535.us.archive.org/2/items/dc_vie_09/dcvie09_mungo_db.ogg

MongoDB website