<p class='tag'>
  <%= label_tag 'Tag' %>
  <%= select_tag("tag[#{tag.id}]", 
        options_from_collection_for_select(
          [nil] + Project.available_tags, 
          'to_s', 
          'to_s',
          @custom_fields[custom_field.id.to_s]
        )
      )
  %>
</p>
