Multiple ajax calls inside a each() function.. then do something once ALL of them are finished?

Use deferred objects:

$("#form").submit(function(e){

    e.preventDefault();

    var calls = [];

    $(".friendName[value!='']").each(function(){
        // Submit the ajax request
        calls.push($.ajax({ 
            type: 'POST', 
            url: 'ajax/url', 
            data: {
                name: name,
                email: email
             },
             success: function(json) {
                // Log a console entry if our ajax request was successful
                console.log(name + " was submitted via ajax");
             }
         }));
    });

    $.when.apply($, calls).then(function() {
        window.location= "https://stackoverflow.com/thanks";
    });
});