Link: http://www.stylusstudio.com/xslt_editor.html
Source Author or Organization: Stylus Studio

The Stylus Studio XSLT Editor provides an advanced editing environment for working with XSLT stylesheets. It works with all of the major commercial and open-source XSLT processors, including MSXML (3.0, 4.0 and 6.0), Microsoft System.XML (1.0 and 2.0), Apache Xalan, Saxon, and many others. You can use the XSLT editor to write both XSLT 1.0 and 2.0 stylesheets, including schema-aware XSLT stylesheets. The Stylus Studio XSLT editor provides Single-Click XSLT Transformation (or press the F5 key) - the XSLT output is automatically displayed in a dockable XSLT output window. In the event of an XSLT processing error, the XSLT editor provides integrated backmapping support, so you can just click on the XSLT error or warning message in the output window and the offending line of XSLT code will be highlighted by the XSLT Editor, thus simplifying XSLT troubleshooting. Finally, the XSLT Editor provides robust XSLT text editing support including code-completion of XSLT and XPath functions, syntax highlighting, and more, providing you with complete control over your XSLT code.