You can create a new file with any extension within Eclipse (File->New->File or equivalent button on toolbar on 3.0M9). Is that what you meant?
The real bugger is there are no native XML or JSP editors - so you don't get syntax highlighting or code completion in JSPs for taglibs and stuff.
I've yet to find a good, free editor for either XML or JSP, though I admit I haven't looked far. The Lomboz J2EE plugin has some JSP facilities but it's massive overkill for the editor alone - I'm running Eclipse on a RAM hungry machine so I try and keep plugins to a minimum.