Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.
XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
Workflowy - A better way to organize your mind.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
Indigrid - Plain text outliner with side-by-side views.
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.