Liquid XML Studio
Full user review
"Great XML Schema Editor"
Very nice XML Schema Editor - easy to see whats going on and editor XSD's
XML Sample generator - great for creating sample XML from an XSD, great for testing
Didn't chameleon scheams
There are better things about, but this does most of what you'd want and for free.
There is also a newer (not so free) version which does do the rest.