Safari has been my browser of choice since forever simply because it’s super-fast. One thing that has annoyed me for a while though is that you can’t just view raw XML like you can in other browsers, without choosing ‘View Source’, or turning on the Web Inspector panel.
In developing some EntityBroker code, with XML as the output, I just get the content. Not too helpful. Fed up, I went searching for a solution, and found an excellent one called XML View Plugin: http://www.entropy.ch/software/macosx/xmlviewplugin/
It’s a plugin that you simply drop into Library > Internet Plug-Ins, restart Safari and can now view the raw XML on screen in all its syntax-coloured glory!
steveswinsburg 
Thanks, this looks like a useful one. Found any that do the same for JSON?
Not yet but I’m looking for one. I seem to be able to view the raw source of a JSON document at the moment in Safari, and for small fragments it’s ok, but some colouring/folding would be good for larger JSON documents.