API List - A collective list of APIs. Build something.
XML Copy Editor - XML Copy Editor is a fast, free, validating XML editor.
The Unsplash API - No-limits, do-what-you-want API for access to 200K+ HD pics.
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.
Abstract APIs - Simple, powerful APIs for everyday dev tasks
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.