gistfile1.js

$.fn.tagList = function() {
  return this.each(function() {
    var $orginal  = $(this),
        $input    = $('<input type="text">'),
        $button   = $('<button class="add_tag">Add</button>'),
        $tag_list = $('<ul class="tags" />'),
        $suggestions  = $orginal.parents('form').find('div.popular.tags'),
        current_value = $orginal.val();
    $orginal.parent()
        .addClass('taggings')
        .prepend($tag_list)
        .append($button)
        .end()
      .replaceWith($input);
    
    $tag_list.data('tags', []);

    $tag_list.bind('add.tags', function(event, value) {
      var tag_items = '';
      $.each(value.split(' '), function() {
        var tag = $.trim(this).toLowerCase();
        if ($.inArray(tag, $tag_list.data('tags')) == -1) {
          $tag_list.data('tags').push(tag);
          tag_items += '<li><span>'+tag+'</span><input type="hidden" name="mash_app[tag_list][]" value="'+tag+'"><a href="#remove_tag" class="remove">-</a></li>';
        }
      });
      $tag_list.append(tag_items);
    }).bind('click.tags', function(event) {
      if (event.target.nodeName.toLowerCase() != 'a') { return; }
      event.preventDefault();
      var $item = $(event.target).parent('li'), 
          tag   = $item.find('span').text(),
          index = $.inArray(tag, $tag_list.data('tags'));
      $tag_list.data('tags').splice(index, 1);
      $item.remove(); // This call generates a "no method or property for object" error in IE
      // this.removeChild(event.target.parentNode) // so does this
    });