Since new coding is pretty much ramped down for SQL Developer , I needed a place to test out some features in a way that everyone can benifit. I've created a project on sourceforge, http://sourceforge.net/projects/esdev. The current extension there enables support for readonly XMLTypes and adds export to excel in native excel inthe worksheet thanks to Poi.
I hope this project also shows how easy it is to extend base functionality. The web cvs isn't working yet but once it is, take a look and see what it took to add this.
If you would like to see these examples in action, add the center.xml to your check for update. The center file is http://osdn.dl.sourceforge.net/sourceforge/esdev/center.xml
I'll probably tinker here with trying to intergrate some open source projects into sql developer.