Open Source Database Management Systems (DBMS)

SQuirreL SQL Client is a graphical SQL client written in Java that will allow you to view the structure of a JDBC compliant database, browse the data in tables, issue SQL commands etc.

Eclipse SQL Client for database querying/browsing any JDBC compliant database. It supports plugins with specialized functionality for individual databases (Oracle, DB2, MySQL, PostgreSQL, Sybase, Informix) and can be extended.

MyWebSQL is a web based WYSIWYG Database client written in PHP. It has a simple and intuitive interface with the look and feel of a desktop application, and offers rich features for database management. No installation is needed, just download, extract and you are ready to go. It even has a single file compact version with full functionality, which you can quickly deploy on your server. Currently MyWebSQL supports working with MySQL, PostgreSQL and SQLite databases.

MongOz is a MongoDB client, intended to be multi-platform. It's written in Java as backend (to handle the MongoDB connections) and Javascript / HTML5 / CSS3 as frontend, in order to have a modern interface, besides being easy to change as desired.