Graphtage is a commandline utility and underlying library for semantically comparing and merging tree-like structures, such as JSON, XML, HTML, YAML, and CSS files.

BaseX is a light-weight, high-performance and scalable XML Database engine and XPath/XQuery 3.1 Processor, which includes full support for the W3C Update and Full Text extensions. An interactive and user-friendly GUI frontend gives you great insight into your XML documents.

Ajax GUI Framework

a simple CMS based on XML standards

GetSimple is an XML based, stand-a-alone, fully independant and lite Content Management System.

OpenXML - Create Excel2007 documents in PHP - Spreadsheet engine

User friendly XML editing software