5. OrientDB
OrientDB is an open source NoSQL database management system written in Java. Even if it is a document-based database, the relationships are managed as in graph databases with direct connections between records. It supports schema-less, schema-full and schema-mixed modes. It has a strong security profiling system based on users and roles and supports SQL as a query languages.
Home: http://www.orientechnologies.com/
Quick Start: http://code.google.com/p/orient/wiki/Tutorials
Download: http://code.google.com/p/orient/wiki/Download

6. ThruDB
Thrudb is a set of simple services built on top of the Apache Thrift framework that provides indexing and document storage services for building and scaling websites. Its purpose is to offer web developers flexible, fast and easy-to-use services that can enhance or replace traditional data storage and access layers.
It supports multiple storage backends such as BerkeleyDB, Disk, MySQL and also having Memcache and Spread integration.
Home: http://code.google.com/p/thrudb/
Quick Start: http://thrudb.googlecode.com/svn/trunk/doc/Thrudb.pdf
Download: http://code.google.com/p/thrudb/source/checkout

7. SisoDB
SisoDb is a document-oriented db-provider for Sql-Server written in C#. It lets you store object graphs of POCOs (plain old clr objects) without having to configure any mappings. Each entity is treated as an aggregate root and will get separate tables created on the fly.
Home: http://www.sisodb.com
Quick Start: http://www.sisodb.com/Wiki
Download: https://github.com/danielwertheim/SisoDb-Provider/

8. RaptorDB
RaptorDB is a extremely small size and fast embedded, noSql, persisted dictionary database using b+tree or MurMur hash indexing. It was primarily designed to store JSON data (see my fastJSON implementation), but can store any type of data that you give it.
Home: http://www.codeproject.com/KB/database/RaptorDB.aspx
Quick Start: http://www.codeproject.com/KB/database/RaptorDB.aspx
Download: http://www.codeproject.com/KB/database/RaptorDB.aspx