(a) Common startup files for emacsen

      /usr/local/etc/emacsen/site-start.d/

(b) Code locations

(b-0) common directory to install emacs lisp files

      /usr/local/share/emacsen/site-lisp/

(b-1) site-package directory for XEmacs

    /usr/local/lib/xemacs/site-packages/{lisp|etc|...}

(b-2) site-lisp directory for GNU Emacs 23

    /usr/local/share/emacs23/site-lisp/