Emacs

My .emacs file mostly defines the FKeys.

The internal-links mode adds a vim-like hypertext system to Emacs.

I also wrote right-wrong-mode, a mode to mark tested/untested sections in a buffer with different colors. However, its not yet up since it needs some polishing.

If you seriously want to edit XML, i strongly urge you to try nXML, James Clark's new XML mode. It includes a RELAX NG schema validator in Elisp! Therefore it knows the allowed elements (if theres a RNC for the document, of course) and can complete tage.

Try it, and you'll never want to write XHTML "by hand" again.