Doxymacs is Doxygen + {X}Emacs.

The purpose of the doxymacs project is to create a LISP package that
will make using Doxygen from within {X}Emacs easier.

It has the following features:

    * ability to look up documentation for symbols from {X}Emacs in
      the browser of your choice.
    * easily insert Doxygen style comments into source.
    * optionally use an "external" (i.e. written in C) XML parser to
      speed up building the completion list.
    * fontify Doxygen keywords.

WWW: http://doxymacs.sourceforge.net/