Please check out the following code
<html>
<head>
<title>tile.stamen.com: OpenLayers</title>
<script type="text/javascript" src="http://www.openlayers.org/api/OpenLayers.js"></script>
<script type="text/javascript" src="http://maps.stamen.com/js/tile.stamen.js?v1.1.2"></script>
<script type="text/javascript">
var map, layer;
function initialize() {
map = new OpenLayers.Map('map', {controls: [new OpenLayers.Control.LayerSwitcher({})]});
stamenLayer = new OpenLayers.Layer.Stamen("toner-lite");
map.addLayer(stamenLayer);
map.setCenter(new OpenLayers.LonLat(-13630355, 4546576), 10);
}
</script>
<style type="text/css">
#map {
width: 800px;
height: 600px;
}
</style>
</head>
<body onload="initialize()">
<div id="map"></div>
</body>