XPath Visualizer
http://www.topxml.com/xpathvisualizer/

This is a full blown Visual XPath Interpreter for the evaluation of any XPath expression and visual presentation of the resulting nodeset or scalar value. The XPath Visualizer’s value as an XSLT and XPath learning and authoring tool results from its ability to present the results of any XPath expression in an immediate, appealing and straightforward visualization. It allows the user to define their own dynamic xsl:variable and xsl:key elements and to use variable references and the key() functions in their XPath expressions. The XPath Visualizer remembers and makes available to manage and reuse any previously entered expression, variable or key definition. The source XML Document is displayed with any node hi-lighted that satisfies the XPath expression. In case the expression evaluates to a scalar (string number boolean) then it is displayed in a separate window. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.