I was searching for some freeware tools for authoring XML and XSD documents. But my bad search inputs didn't return any good results.
So I planned out to create this tooling myself. I decided to use Eclipse as the platform for this, as it is quite robust and very popular.
After few days of effort, I ended up with a very basic prototype. The details are available at, http://gandhimukul.tripod.com/xml/xmleclipse.html. But still lot of work needs to be done on this code base to make it really useful for XML developers, particularly the content assist functionality which is presently missing.
I posted my thoughts about this on xml-dev list.
Dave Carver on xml-dev list suggested to me that there already exists such a tooling. It's the "Web Tools Platform (WTP)" for Eclipse.
I gave WTP a try. Personally speaking, I found it very good. It already has lot's of things that I need in XML GUI tools. Moreover, it's free and open source.
I have now kept WTP in my toolset to author XML, XSD and DTD documents. If required, I might try to tweak it's source code to do something new.