eXist eXist is an Open Source repository and retrieval engine for XML documents. http://exist.sourceforge.net/

Lore Lore is a database management system (DBMS) for XML. The Lore executables are available for public use. http://www-db.stanford.edu/lore/

interBasis (IB 2.x) SGML/XML-savy structured fulltext engine and multi-protocol information management system. (BSn) http://www.bsn.com/Z39.50/

Xindice DBMS written in Java to optimize the storage, retrieval, querying, and management of XML-based documents. Xindice was known as "dbXML Core" prior to joining the Apache XML Project. http://xml.apache.org/xindice/

Castor Open source data binding framework for Java with support for XML, SQL, LDAP, and JDO. http://castor.exolab.org/

Jena semantic web toolkit java API for manipulating RDF models, uses Berkeley DB (Sleepycat) for storage and also offers support for relational databases http://www.hpl.hp.com/semweb/jena-top.html