gistfile1.rb

## _form.html.erb ##

<%= link_to(image_tag(element.element_data.url(:thumb)), portfolio_add_element_path(element), :remote=>true) %>

## Portfolios_Controller.rb ##
  respond_to :js, :html

  def add_element
    @portfolio = Portfolio.find(portfolio_id)
    @element = Element.find(element_id)
    @portfolio.elements.create(@element)
    respond_with(@portfolio) do |format|
      # You don't want to redirect when you come from an ajax call.
      format.html { redirect_to (@portfolio) }
    end
  end