XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
Exstora - Built-in quick note: save ideas, contacts, interesting facts
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
OneNote Online - OneNote Online, part of Office Online, is the online version of Microsoft OneNote.
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.
Nikabot - A Slackbot that keeps track of what your team is doing so you don't have to.