Note that soon after this answer was originally posted, Apache XMLBeans was retired. As such, I cannot recommend it anymore. Anyway, I am still of the opinion that it had good command line support for generating example xsd:s, but a new release haven't been done in well over 2 years at time of writing.
command line based is ofcourse the preferred method!
In my opinion xsd2inst in the Apache XMLBeans is a very good tool for this. It is command line based and ships with binaries for Windows and Unix/Linux.
It is really simple to use too:
xsd2inst schemafile.xsd -name globalElementName
It generates the output directly to the console and can of course easily be piped to a file.
Is there an IDE out there that can generate XML from XSD?
IntelliJ Idea has the same functionality if using an IDE is prefered, even in the community edition. Just right click inside the xsd document and select Generate Instance Document From Schema, then select the root node.