Leaflet

<div id="map"></div>
<script type="text/javascript">
	var map = L.map('map').setView([51.505, -0.09], 13);

	L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
	    attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
	}).addTo(map);

	L.marker([51.5, -0.09]).addTo(map)
	    .bindPopup('A pretty CSS3 popup.<br> Easily customizable.')
	    .openPopup();
</script>