GMaps.js allows to add KML and GeoRSS layers:
infoWindow = new google.maps.InfoWindow({});
map.loadFromKML({
url: 'http://www.searcharoo.net/SearchKml/newyork.kml',
suppressInfoWindows: true,
events: {
click: function(point){
infoWindow.setContent(point.featureData.infoWindowHtml);
infoWindow.setPosition(point.latLng);
infoWindow.open(map.map);
}
}
});
Note: You can learn more about KML and GeoRSS layers here.