http://jsfiddle.net/matt_eggcartel/3pXXF/19/

^ js fiddle link

var markerArray = [];

var dots = [
[0, -1, "A"],
[0, -2, "B"],
[0, -3, "C"],

];

function initialize() {
var latlng = new google.maps.LatLng(0, 0);

var myOptions = {
zoom: 6,
center: latlng,
mapTypeId: google.maps.MapTypeId.ROADMAP
};

var map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
var image = 'i/hotel-map-pin.png';

var mc = new MarkerClusterer(map, marker);

google.maps.event.addListener(map, 'click', function() {
infowindow.close();
});

for (var i = 0; i < dots.length; i++) {
var marker = new google.maps.Marker({
position: new google.maps.LatLng(dots[i][0], dots[i][1]),
map: map,
title: dots[i][2]


});
mc.addMarkers(markerArray, true);
}

}
window.onload = initialize;