AntTask-GenerateXML is an Ant task that uses XMLBeans to create example XML instances from a W3C schema. It is especially useful for looking at pieces of schema, as you can set the element you wish to use as the root one. It will use the values from enumerations as the fixed/default values for attributes and elements if they are set. It obeys the XML type system with the exception of regex/patterns.
XmlPlus xsd2cpp is a tool that compiles an XML schema into C++ data bindings. When invoked on an input XSD file, it generates the C++ sources (implementation/headers) for the supplied XML schema, a main.cpp template to demonstrate how generated sources can be consumed, and the automake/autoconf files for building the generated source.