The Google Maps API 

• Javascript

• Data as XML or JSON

• Requires an API Key, bound to a particular directory on your domain.

function new_marker() {
    if ( typeof current != 'undefined' ) {
        map.removeOverlay( current );
    }

    var center = map.getBounds().getCenter();
    current = new google.maps.Marker(center, {'title': 
    'Move to place...', 'draggable': true, 'bouncy': true});

    google.maps.Event.addListener(current, "dragend", function() {
        click(current.getPoint());
    });
    map.addOverlay( current );

    $('lat').value = current.getPoint().lat();
    $('lng').value = current.getPoint().lng();
}