Berkeley DB Java Edition
a high performance, transactional storage engine written entirely in Java. Like the highly successful Berkeley DB product, Berkeley DB JE executes in the address space of the application, without the overhead of client/server communication. It stores data in the application's native format, so no runtime data translation is required. Berkeley DB JE supports full ACID transactions and recovery. It provides an easy-to-use interface, allowing programmers to store and retrieve information quickly, simply and reliably.
HSQLDB is a relational database engine written in Java, with a JDBC driver, supporting a subset of ANSI-92 SQL. Read more
a free Java application designed to store and manage data in any format that the user defines. Instead of having multiple applications to manage passwords, music databases, shopping lists, etc, JCards allows the user to define a database that contains the fields they want and to customise it in many ways
a port of the extremely popular MySQL relational database to the Zaurus Read more
the first Italian Open Source relational database management system
PortaBase is a small database program for creating, browsing, and editing custom tables of data on the Sharp Zaurus and other Linux/Qtopia-based PDAs. Typical uses are media inventories, and reference charts.