Simple Leaflet MarkerCluster example with random GeoJSON data. (Leaflet 0.7.0 test)

HTML

<script src="http://cdn.leafletjs.com/leaflet-0.7/leaflet.js"></script>
<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7/leaflet.css">
<link rel="stylesheet" href="https://rawgit.com/Leaflet/Leaflet.markercluster/leaflet-master/dist/MarkerCluster.css">
<link rel="stylesheet" href="https://rawgit.com/Leaflet/Leaflet.markercluster/master/dist/MarkerCluster.Default.css">
<script src="https://rawgit.com/Leaflet/Leaflet.markercluster/leaflet-master/dist/leaflet.markercluster.js"></script>
<div id="map"></div>

CSS

html, body, #map {
    height: 100%;
    width:100%;
    padding:0px;
    margin:0px;
    background: white;
}
.info {
    padding: 6px 8px;
    font: 14px/16px Arial, Helvetica, sans-serif;
    background: white;
    background: rgba(255, 255, 255, 0.8);
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
    border-radius: 5px;
}
.info h4 {
    margin: 0 0 5px;
    color: #777;
}
.legend {
    text-align: left;
    line-height: 18px;
    color: #555;
}
.legend i {
    width: 18px;
    height: 18px;
    float: left;
    margin-right: 8px;
    opacity: 0.7;
}
.legend .colorcircle {
    border-radius: 50%;
    width: 15px;
    height: 15px;
    margin-top: 0px;
}
.legend .circlepadding {
    border-radius: 50%;
    margin-top: 0px;
    background: rgba(255, 255, 255, 0.8);
}

JavaScript

//***************************************************************************//
//BEGINNING of old markercluster code
//***************************************************************************//

/*
 Leaflet.markercluster, Provides Beautiful Animated Marker Clustering functionality for Leaflet, a JS library for interactive maps.
 https://github.com/Leaflet/Leaflet.markercluster
 (c) 2012-2013, Dave Leaver, smartrak
*/
(function (window, document, undefined) {
/*
 * L.MarkerClusterGroup extends L.FeatureGroup by clustering the markers contained within
 */

L.MarkerClusterGroup = L.FeatureGroup.extend({

	options: {
		maxClusterRadius: 80, //A cluster will cover at most this many pixels from its center
		iconCreateFunction: null,

		spiderfyOnMaxZoom: true,
		showCoverageOnHover: false,
		zoomToBoundsOnClick: true,
		singleMarkerMode: false,

		disableClusteringAtZoom: null,

		// Setting this to false prevents the removal of any clusters outside of the viewpoint, which
		// is the default behaviour for performance reasons.
		removeOutsideVisibleBounds: true,

		//Whether to animate adding markers after adding the MarkerClusterGroup to the map
		// If you are adding individual markers set to true, if adding bulk markers leave false for massive performance gains.
		animateAddingMarkers: false,

		//Increase to increase the distance away that spiderfied markers appear from the center
		spiderfyDistanceMultiplier: 1,

		//Options to pass to the L.Polygon constructor
		polygonOptions: {}
	},

	initialize: function (options) {
		L.Util.setOptions(this, options);
		if (!this.options.iconCreateFunction) {
			this.options.iconCreateFunction = this._defaultIconCreateFunction;
		}

		this._featureGroup = L.featureGroup();
		this._featureGroup.on(L.FeatureGroup.EVENTS, this._propagateEvent, this);

		this._inZoomAnimation = 0;
		this._needsClustering = [];
		this._needsRemoving = []; //Markers removed while we aren't on the map need to be kept track of
		//The bounds of...