With GMaps.js you can use a marker clusterer to group large amount of markers:
map = new GMaps({
div: '#map',
lat: -12.043333,
lng: -77.028333,
markerClusterer: function(map) {
return new MarkerClusterer(map);
}
});
You can use MarkerClusterer or MarkerClustererPlus. If you want to use a custom marker clustering library, you have to define a addMarker method.
Note: Read more about MarkerClusterer and MarkerClustererPlus here.