Here is some code that shows how to use an XML file to load multiple markers. Also this site is the best there is for Google Maps examples and tutorials
// A function to create the marker and set up the event window
function createMarker(point,name,html) {
var marker = new GMarker(point);
GEvent.addListener(marker, "click", function() {
marker.openInfoWindowHtml(html);
});
// save the info we need to use later for the side_bar
//gmarkers.push(marker);
// add a line to the side_bar html
//side_bar_html += '<a href="javascript:myclick(' + (gmarkers.length-1) + ')">' + name + '<\/a><br>';
return marker;
}
// This function picks up the click and opens the corresponding info window
function myclick(i) {
GEvent.trigger(gmarkers[i], "click");
}
$(document).ready(function(){
// When class .map-overlay-right is clicked map is loaded
$(".map-overlay-right").click(function () {
var map = new GMap2(document.getElementById('map-holder'));
$("#map-holder").fadeOut('slow', function(){
var gmarkers = [];
map.addControl(new GSmallMapControl());
map.addControl(new GMapTypeControl());
// Get XML file that contains multiple markers
$.get("http://www.foo.com/xml-feed-google-maps",{},function(xml) {
$('marker',xml).each(function(i) {
// Parse the XML Markers
html = $(this).text();
lat = $(this).attr("lat");
lng = $(this).attr("lng");
label = $(this).attr("label");
var point = new GLatLng(lat,lng);
var marker = createMarker(point,label,html);
map.addOverlay(marker);
});
});
});
$("#map-holder").fadeIn('slow');
var Asia = new GLatLng(19.394068, 90.000000);
map.setCenter(Asia, 4);
});
});