Hi upyup,
It took me a while realize that you forgot to put the echo before $mymap->display( ); and you can remove the var_dump($mymap->pois);
It should look like the following :
$mymap = new Mappress_Map( array( "width" => 600, "height" => 450 ) );
$mypoi = new Mappress_Poi( array( 'address' => $address[0], 'title' => "", 'body' => $address[0] ) );
$mypoi->geocode( );
$mymap->pois = array($mypoi);
echo $mymap->display( );