The following packages appear to be using gnulib and gnulib-tool:

  hello          http://cvs.savannah.gnu.org/viewcvs/hello/?root=hello
  m4             http://cvs.savannah.gnu.org/viewcvs/m4/?root=m4
  libidn         http://josefsson.org/cgi-bin/viewcvs.cgi/libidn/
  shishi         http://josefsson.org/cgi-bin/viewcvs.cgi/shishi/
  gsasl          http://josefsson.org/cgi-bin/viewcvs.cgi/gsasl/
  gnutls         http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/gnutls/?root=GNU+TLS+Library
                 http://josefsson.org/cgi-bin/viewcvs.cgi/gnutls/?root=gnupg-mirror
  libtasn1       http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/libtasn1/?root=GNU+TLS+Library
                 http://josefsson.org/cgi-bin/viewcvs.cgi/libtasn1/?root=gnupg-mirror
  libksba        http://josefsson.org/cgi-bin/viewcvs.cgi/libksba/?root=gnupg-mirror
  gss            http://josefsson.org/cgi-bin/viewcvs.cgi/gss/
  libntlm        http://josefsson.org/cgi-bin/viewcvs.cgi/libntlm/
  libiconv       http://libiconv.cvs.sourceforge.net/libiconv/libiconv/
  gettext        http://cvs.savannah.gnu.org/viewcvs/gettext/?root=gettext
  findutils      http://cvs.savannah.gnu.org/viewcvs/findutils/?root=findutils
  cvs            http://cvs.savannah.gnu.org/viewcvs/cvs/ccvs/
  inetutils      http://cvs.savannah.gnu.org/viewcvs/inetutils/?root=inetutils
  gpg            http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/trunk/
  pspp           http://cvs.savannah.gnu.org/viewcvs/pspp/?root=pspp
  msmtp          http://msmtp.cvs.sourceforge.net/msmtp/msmtp/
  libpreludedb   https://trac.prelude-ids.org/browser/trunk/libpreludedb/
  icoutils       http://riva.ucam.org/svn/cjwatson/src/debian/icoutils/trunk/icoutils/
  OPeNDAP        http://scm.opendap.org:8090/svn/trunk/
  miktex         https://svn.sourceforge.net/svnroot/miktex/miktex/trunk
  newts          http://svn.arete.cc/newts/trunk/
  libdap         http://scm.opendap.org:8090/svn/trunk/libdap/
  Net::CDP       http://search.cpan.org/src/MCHAPMAN/Net-CDP-0.09/libcdp/

The following packages appear to be using gnulib without gnulib-tool:

  coreutils

Articles:

  "Using Gnulib to improve software portability"
  http://programming.linux.com/programming/05/12/16/2051201.shtml?tid=67