Some of XML/XSLT/XML-RPC related stuff for the mac (found at Todd Ditchendorf’s) site:

• Cocoatron :: Automator Actions for XML Processing Pipelines
  The suite of Automator Actions for Mac OS X that brings drag-and-drop simplicity to creating and automating complex XML Processing Pipelines.
  (tags: software macosx applescript xml cocoatron)
• TeXMLMate :: XML/DTD/XSD/RNG Plugin for TextMate
  Check XML and XHTML documents for Well-Formedness and Validity while editing them in TextMate with support for DTD, W3C XML Schema, RELAX NG, Schematron and XInclude.
  (tags: software macosx textmate plugin xml texmlmate)
• Cocoa XML-RPC Client
  XML-RPC Client is a free Cocoa-based developer tool for Mac OS X Tiger that allows you to access and debug XML-RPC web services from the comfort of your desktop.
  (tags: software macosx xmlrpc cocoa)
• OttoMate
  The Suite of Mac OS X Automator Actions that mates the simple, intuitive beauty of the Aqua Graphical User Interface with Automated Web Testing.
  (tags: software macosx automator web testing ottomate)