SQLite

SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. SQLite is the most widely deployed SQL database engine in the world.

License: Public Domain
Written in: C
Operating system: Cross-platform

Website: http://www.sqlite.org/
Download: http://www.sqlite.org/download.html
Documentation: http://www.sqlite.org/docs.html