//usage:
google.load('maps', '3', {other_params:'sensor=false', "callback" : _deferred.resolveCallback('gmap')}); 
(function(d){
    var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
    if (d.getElementById(id)) {return;}
    js = d.createElement('script'); js.id = id; js.async = true;
    js.src = "//connect.facebook.net/en_US/all.js";
    ref.parentNode.insertBefore(js, ref);
}(document));

// Init the SDK upon load
window.fbAsyncInit = function() {
    FB.init({
        appId      : XXX      
    });
    _deferred.resolve('facebook');
};

//do some stuff after google maps load:
_deferred.done('gmap', function(){
   ... 
});

//do some stuff after google maps and facebook load:
_deferred.done(['gmap', 'facebook'], function(){
   ... 
});