Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
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.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
Trelby - The free, multiplatform, feature-rich screenwriting program!
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.