XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
MarkLogic - Schema-agnostic Enterprise NoSQL database technology, coupled w/ powerful search & flexible application services
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.
Apache Xerces - Advanced XML parser, including support for XML Schema, DOM Level 2, and SAX.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
Qizx - XML Databases