A couple of years ago I wrote a blog entry about how to install the missing XML Schema Editor and related utilities from the dev update center in Netbeans 6.9. Now there is a unofficial update center:
It contains the development branches of these and instructions on how to install, thanks to Geertjan Wielenga.
I installed the plugin on Netbeans 7.1 [update: I installed it also in 7.2] and it seems to work, even if I did not test it intensively, primarily because these days I'm no more working that much with XML Schemas and WSDL files.
There is an apparently disabled Hudson project for the XML Tools. Now, if you want to put this nice plugin back into the regular plugin repository, please vote for this issue!