Fix for js2's horrible indentation. I'd be willing to have this guy's babies.

" ... Sepia is a set of tools for Perl development in Emacs. Its goal is to extend CPerl mode to support fast code navigation and interactive development. It is inspired by Emacs' current support for a number of other languages, including Lisp, Python, and Emacs Lisp ... "

Discusses several approaches for using multiple major-modes in a single buffer (for, for example, literate programming). 'multi-mode' seems to be the most promising approach, as it maintains several 'shadow' buffers behind the scenes to avoid switching modes and keymaps all the time. It is incompatible with nXML font-locking and (presumably) js2-mode, though.

Recursive-descent parser based XML editing mode. Syntax highlighting, and more importantly, support XHTML very well.

Recursive-descent parser-based editing mode for emacs. Does syntax highlighting, shows warnings. Not as comprehensive as espresso-mode + flymake + jslint, probably, but good enough.