Oracle has a huge repository of resources located at http://otn.oracle.com. Your first stop should be the XML Technology Center, located at http://otn.oracle.com/tech/xml. This is the location of the following resources:
Oracle XML Developer’s Kits documentation and releases
XDK and XML DB forums
XDK and XML DB samples, tutorials, and technical papers
XML Technology Preview releases (current XQuery and StAX parser)
You can also find development versions of the latest Oracle product releases at OTN, such as the following:
Oracle Database 10g, at http://otn.oracle.com/products/database/
Oracle Application Server 10g, at http://otn.oracle.com/products/ias/
Oracle JDeveloper 10g, at http://otn.oracle.com/products/jdev/