Open source high-performance database system developed at CWI, the Institute for Mathematics and Computer Science Research of The Netherlands. http://monetdb.cwi.nl/
ChurchInfo is a php/mySQL database to keep track of people, families, groups, pledges and payments, sunday school classes, etc. http://www.churchdb.org
Provides small footprint, high performance, and easy-to-use embedded database solutions. Also sells technical support and consulting. http://www.ittia.com/
An integrated environment for managing data. It helps creating database schemas, inserting, querying and processing data. Screenshots, downloads, resources, a wiki and a list of involved developers. http://www.kexi-project.org/
The Ocelot SQL DBMS adheres closely to the ANSI/ISO SQL standard. The site has software downloads, tutorial information, and reviews of SQL or general DBMS books. [Mozilla and GPL] http://www.ocelot.ca
Download a web-based, open-source version of Microsoft's Enterprise Manager for SQL Server that can be used to administrate SQL Server and MSDE with a web browser. http://www.aspenterprisemanager.com/