Here is the XEmbed protocol support I wrote last year [1].  RMS asked me to
bring it up again after the release of Emacs 22 [2].

[1] http://lists.gnu.org/archive/html/emacs-devel/2006-02/msg00017.html
[2] http://lists.gnu.org/archive/html/emacs-devel/2006-02/msg00162.html

There are five incremental patches plus one additional one
(gtk-scrollbar-position) which I like for aesthetic reasons.  The code
hasn't been changed since the last submission (if I remember correctly), but
I've regenerated the patches against 22.1.  The patches can also be viewed
in a Git repository at http://timo.stc.cx/git/?p=emacs-xembed.git .

timo