Altova XMLSpy - The XMLSpy XML Editor is a powerful tool for editing XML and related technologies. It is the only XML Editor with patented SmartFix validation, enterprise-grade editors, converters, debuggers, and code generators.
XMLBlueprint - XMLBlueprint is the smart and lightweight XML editor for Windows.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
TreeLine - TreeLine just stores almost any kind of information.
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.
XPontus XML Editor - XPontus XML Editor is a simple XML Editor oriented towards text editing.