ODBTP (Open Database Transport Protocol) provides remote ODBC access to databases for client applications where local ODBC access is unavailable or inadequate.
The XML:DB project (http://www.xmldb.org) defines an XML database interface called XML Database API. This project aims to create interfaces implementing the XML Database API which connect via SOAP to databases that implement the XML Database API.
jDB is a small, lightweight, easily embeddable into other applications database system that has a console frontend to use to manage your own personal data, and a CGI frontend to administer and use remote databases through the web.