Viewing an older version of mapbox.js. Check out v1.4.0 for the latest.

Creating a map with multiple layers with mapbox load

Simple loader
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Creating a map with multiple layers with mapbox load</title>
  <script src='http://api.tiles.mapbox.com/mapbox.js/v0.6.7/mapbox.js'></script>
  <link href='http://api.tiles.mapbox.com/mapbox.js/v0.6.7/mapbox.css' rel='stylesheet' />
  <style>
    body { margin:0; padding:0; }
    #map { position:absolute; top:0; bottom:0; width:100%; }
  </style>
</head>
<body>
<div id='map'></div>
<script>
    mapbox.load(['examples.map-zr0njcqy', 'examples.map-9ijuk24y'], function(data) {
        var map = mapbox.map('map');

        map.ui.zoomer.add();

        // After specifying multiple ids to mapbox.load, you'll get an array
        // of data objects back, with pre-initialized layer and markers members
        map.addLayer(data[1].layer);
        map.addLayer(data[0].markers);

        // Zoom and center the map
        map.zoom(11).center(data[0].center);

        // Attribute map
        map.ui.attribution.add()
            .content('<a href="http://mapbox.com/about/maps">Terms &amp; Feedback</a>');
    });
</script>
The code and documentation to mapbox.js is hosted on GitHub where you can contribute changes and improvements.