nXML-mode: How XML should Work
James Clark, writer of expat, editor of the XSLT Recommendation and all-round XML genius, has done it again, by writing an XML editing mode for Emacs that doesn't suck. In all fairness, PSGML-mode isn't terrible - I wouldn't have been using it daily for the last few years if it was - but it was an SGML editor with XML functionality bolted on, which meant it was unnecessarily complicated, and couldn't do anything useful without a DTD. nXML-mode is still in alpha, and doesn't have a pretty download page yet, but is nevertheless the bee's knees, the dog's bollocks, and almost any other part of any animal you'd care to name (except, perhaps, the dingo's kidneys). It's based on RELAX NG schemas (and comes with XHTML, XSLT and DocBook out of the box), works fine without any validation, supports namespaces, and autocompletes like a dream. Hoorah!
(It may seem like I'm getting a little overexcited about Yet Another Emacs Mode, but I'm getting my head down to write my thesis, and hence will be writing even more XML than usual over the next few months, so I welcome this like a plumber would welcome a new, revolutionary sort of self-assembling pipe. Or something.)