Foursquare API call (from @tmcw)

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>#BTV Places from Foursquare</title>

// Credit Foursquare for their wonderful data
map.attributionControl
    .addAttribution('<a href="https://foursquare.com/">Places data from Foursquare</a>');

// Create a Foursquare developer account:
// https://developer.foursquare.com/
// AND CHANGE THESE VALUES TO YOUR OWN:
// otherwise they can be cycled or deactivated with zero notice.
var CLIENT_ID = 'L4UK14EMS0MCEZOVVUYX2UO5ULFHJN3EHOFVQFSW0Z1MSFSR';
var CLIENT_SECRET = 'YKJB0JRFDPPSGTHALFOEP5O1NDDATHKQ2IZ5RO2GOX452SFA';

// https://developer.foursquare.com/start/search
var API_ENDPOINT = 'https://api.foursquare.com/v2/venues/search' +
  '?client_id=CLIENT_ID' +
  '&client_secret=CLIENT_SECRET' +
  '&v=20130815' +
  '&ll=LATLON' +
  //This is the "cafe" category:
  '&categoryId=4bf58dd8d48988d16d941735' +
  //Uncomment this query to find specific cafe names:
  //'&query=cafe, coffee' +
  '&callback=?';

// Keep our place markers organized in a nice group.
var foursquarePlaces = L.layerGroup().addTo(map);

// Use jQuery to make an AJAX request to Foursquare to load markers
// data.
$.getJSON(API_ENDPOINT
    .replace('CLIENT_ID', CLIENT_ID)
    .replace('CLIENT_SECRET', CLIENT_SECRET)
    .replace('LATLON', map.getCenter().lat +
        ',' + map.getCenter().lng), function(result, status) {

if (status !== 'success') return alert('Request to Foursquare failed');

// Transform each venue result into a marker on the map.
    for (var i = 0; i < result.response.venues.length; i++) {
      var venue = result.response.venues[i];
      var latlng = L.latLng(venue.location.lat, venue.location.lng);
      var marker = L.marker(latlng)
        .setIcon(L.mapbox.marker.icon({'marker-symbol': 'cafe', 'marker-color': 'FFA500'}))
        .bindPopup('<h2><a href="https://foursquare.com/v/' + venue.id + '">' +
            venue.name + '</a></h2>')
        .addTo(foursquarePlaces);
    }

});
</script>

</body>
</html>

Modified http://code.jquery.com/jquery-1.10.1.min.js to a secure url

https://api.tiles.mapbox.com/mapbox.js/v1.6.1/mapbox.js

https://code.jquery.com/jquery-1.10.1.min.js