myXMLDB is a XML database server implemented on top of MySQL. It stores documents as BLOBs and can store documents up to 256 MB in size. It supports XPath and XQuery through Saxon and provides a Java implementation of the XML:DB API. Have GUI interface.
The nasca-db is an xml database server (working on document level). Documents (XML and nonXML) are stored in BerkelyDBXML and can be queried by XPath (later XQuery) and modified by XUpdate. Transactions, replication, locking and logging are full suported
A lightweight versatile XQuery engine in Java, that is standards compliant and can efficiently evaluate XQueries on various containers of data -- even normal Java objects.