var map = {
	init: function(){
		var $map = $('#map');
		var config = {
			zoom: 9,
			center: new google.maps.LatLng(52.376063,0.251936),
			mapTypeId: google.maps.MapTypeId.ROADMAP
		};
		var map = new google.maps.Map(document.getElementById("map"),config);
		switch($map.parent().attr('id')){
			case 'hf':
			  	var markers = [
					["Cambridge", "Queen Anne House", "Gonville Place<br />Cambridge<br />CB1 1ND", "52.20078", "0.12938"], 
					["Peterborough", "The Cresset", "Rightwell<br />Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"]
				];	
			  break;
			default:
			  	var markers = [
					["Cambridge", "Queen Anne House", "Gonville Place<br />Cambridge<br />CB1 1ND", "52.20078", "0.12938"], 
					["Peterborough", "The Cresset", "Rightwell<br />Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"],
					["Peterborough", "Haward House", "Rightwell<br />East Bretton<br />Centre Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"],
					["Peterborough", "Time Stop", "101 Wellington Street<br />Eastgate<br />Peterborough<br />PE1 5DU", "52.57414", "-0.23098"],
					["Wisbech", "Wisbech", "4-6 Stermyn Street<br />Wisbech<br />Cambridgeshire<br />PE13 1EQ", "52.66388", "0.16319"]
				];	
		}
		this.markers(map, markers);
	},
	markers: function(map, markers){
		var infowindow = new google.maps.InfoWindow();
		for(var i=0;i<markers.length;i++) {	
			var city = markers[i][0], name = markers[i][1], address = markers[i][2];
			var latlngset = new google.maps.LatLng(markers[i][3], markers[i][4]);
			var marker = new google.maps.Marker({  
				map: map,  
				title: name,
				icon: folder+'/img/contact-marker.png',  
				position: latlngset,
				content: '<div class="infowindow"><strong>' + city + '</strong><p>' + name + '<br />' + address + '</p><a href="http://maps.google.com/?daddr=' + address.replace(/<br\s*[\/]?>/gi,',') + '" target="_blank">Get Directions</a></div>'
			});
			google.maps.event.addListener(marker, 'click', function () {
				infowindow.setContent(this.content);
				infowindow.open(map, this);
			});
	    }
	}
};

var map = {
	init: function(){
		var $map = $('#map');
		var config = {
			zoom: 9,
			center: new google.maps.LatLng(52.376063,0.251936),
			mapTypeId: google.maps.MapTypeId.ROADMAP
		};
		var map = new google.maps.Map(document.getElementById("map"),config);
		switch($map.parent().attr('id')){
			case 'hf':
			  	var markers = [
					["Cambridge", "Queen Anne House", "Gonville Place<br />Cambridge<br />CB1 1ND", "52.20078", "0.12938"], 
					["Peterborough", "The Cresset", "Rightwell<br />Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"]
				];	
			  break;
			default:
			  	var markers = [
					["Cambridge", "Queen Anne House", "Gonville Place<br />Cambridge<br />CB1 1ND", "52.20078", "0.12938"], 
					["Peterborough", "The Cresset", "Rightwell<br />Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"],
					["Peterborough", "Haward House", "Rightwell<br />East Bretton<br />Centre Bretton<br />Peterborough<br />PE3 8DX", "52.58930", "-0.28354"],
					["Peterborough", "Time Stop", "101 Wellington Street<br />Eastgate<br />Peterborough<br />PE1 5DU", "52.57414", "-0.23098"],
					["Wisbech", "Wisbech", "4-6 Stermyn Street<br />Wisbech<br />Cambridgeshire<br />PE13 1EQ", "52.66388", "0.16319"]
				];	
		}
		this.markers(map, markers);
	},
	markers: function(map, markers){
		var infowindow = new google.maps.InfoWindow(),$subnav = $('.map').find('.subnav');
		for(var i=0;i<markers.length;i++) {	
			var city = markers[i][0], name = markers[i][1], address = markers[i][2];
			var latlngset = new google.maps.LatLng(markers[i][3], markers[i][4]);
			var marker = new google.maps.Marker({  
				map: map,  
				title: name,
				icon: folder+'/img/contact-marker.png',  
				position: latlngset,
				content: '<div class="infowindow"><strong>YMCA ' + city + '</strong><p>' + name + '<br />' + address + '</p><a href="http://maps.google.com/?daddr=' + address.replace(/<br\s*[\/]?>/gi,',') + '" target="_blank">Get Directions</a></div>'
			});
			google.maps.event.addListener(marker, 'click', function () {
				infowindow.setContent(this.content);
				infowindow.open(map, this);
			});
	    }
	}
};

Multiple markers function for Google Maps API V3

Google Maps Multiple Markers

jQuery