You may want to put the following into your /etc/rc.local:

# start wwwoffle
if [ -x ${PREFIX}/sbin/wwwoffled ]; then
        echo -n ' wwwoffled'
        ${PREFIX}/sbin/wwwoffled -c /var/spool/wwwoffle/wwwoffle.conf \
        -p > /var/run/wwwoffled.pid
fi

in /etc/ppp/ppp.linkup:

   !bg ${PREFIX}/bin/wwwoffle -online

in /etc/ppp/ppp.linkdown:

   !bg ${PREFIX}/bin/wwwoffle -offline

Read ${PREFIX}/share/doc/wwwoffle/* for further information.