Editing XML?
There was a question on our internal mailing list today on our translation methods - the answers are in the user guide but the interesting thing was a mail from another BIPper. Microsoft have released a pretty decent XML editor at last. Last time I tried it, it was not a good experience, there still seem to be some niggly issues but overall its pretty useful.

Its not a style sheet editor but if you need to do some work with XML - I seem to spend my life doing this, debugging templates, building demo XML, etc. I get to use the great but expensive, XMLSpy but considering the features I use, the MS solution is pretty good. Get it here:
http://msdn2.microsoft.com/en-us/xml/default.aspx
Here's another 'Open XML Editor' - pretty good, not quite as sophisticated as the MS offering. And another from Peter, better than the Open XML and more on a par with MS.
Of course, if you have jdeveloper installed you get an XML editor included - but if you do not have it anyway, its a bit of an overhead if all you want to do is work with XML files.