jsXe is the Java Simple XML Editor.

jsXe is a fast, intuitive, scalable, platform-independent XML editor It is written in Java using the Swing toolkit, and Xerces-J and is released under the terms of the GNU General Public License. It aims to provide end users and developers with an intuitive way of creating XML documents that is simple enough to deal with any XML document but flexible to allow the addition of support for XML document formats through the use of plugins.

URL: http://jsxe.sourceforge.net/
Licence: GPL