XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.
Online XML Editor - Guide to learn programming
Stylus Studio - Stylus Studio® 2010 XML Enterprise Suite is an advanced XML Integrated Development Environment...
XML Marker - A fast and easy source-level XML and Json Editor, XML Marker uses a combination of syntax-highlighting editor, tree view, and table views to help you get a better insight to your XML code