For all you Oracle database and Java developers out there, here's a fun mashup that combines an Oracle database (with its XML DB feature that can generate XML dynamically), a Java Servlet to extract the XML data, and the Google Maps API to provide a compelling, Map based user interface to the data.
This example allows users to query a database of fictitious worldwide hotels from a Google Maps application. A simple form passes query parameters with hotel attributes to a Java Servlet which in turns executes the database query and generates geocoded hotel data in XML using Oracle's XML DB feature.
The Web client uses GDownloadUrl to retrieve the XML data. An associated callback function then displays it on the map using markers and infoWindows.
A full writeup of this fun Mashup, including downloadable source code, is available at Oracle's Technology Network website.