Here is a (short) list of freeware tools to help you create Blue Cat's skins. You can do everything with Microsoft Windows 'Notepad' and 'Paint', but a good XML editor and an image manipulation program will simplify the task!
You can simply view XML with Microsoft Internet Explorer. It shows a formatted and indented text view of an XML file. Just double click on the skin file and it will be opened with Microsoft IE.
To view and edit XML files, a very simple editor is MindFusion's XML Viewer (freeware). Screen shots of this program will be used in this document to have a clearer view of the skins structure. It allows users to create XML files without knowing anything about XML syntax.
Notepad 2, an extended notepad text editor which includes XML syntax highlighting.
Pov-Ray 3D Ray tracer is a very simple freeware tool to create 3D Graphics.
The GIMP is a reference tool for image manipulation.
IrfanView is very simple for basic image operations, and its batch processing functionality is really awesome.
TrentStitch (apparently discontinued by the author, but it can be found here or here) enables you to create 'film strip' images from multiple files. Very useful to create knob or button widgets.