Does anyone know a quick and easy way (or a tool) to generate hbm.xml files for objects described in a WSDL file?

Sure code up a custom dialect for the reveng tool set.
I have started writing a blog entry on this little know feature.

Great! What's the URL of your blog?

When I finish it. It will be up on the Hibernate shared blog. Link is on hibernate front web page. It should be done soon and I will get Max to review it etc. I have a very sick family member at the moment plus work etc I will do my best to get it complete ASAP. In the mean time check the tools, look for the JDBC Meta data Dialect. I recently commit a specialised Oracle Meta data Dialect using the interface. This will give you the foundation so instead of a SQL query you would use XStream or SAX etc to parse the XML.