jQuery 1.3 ßeta(blog.jquery.com)

    // Returns this or closest ancestor that matches selector
    $(this).closest("div");

    // Will handle clicks on all elements that match selector
    // even if new ones are added later
    $("#foo > div").live("click", someFn);

    $.ajax({
      beforeSend: function(xhr){
        xhr.setRequestHeader("Accept","application/json");
      },
      ... other options ...
    });