Since I didn\'t get the expected answer on my last question I\'ll try to simplify and narrow my question:
How can I build a dropdown-menu that uses AJ
How about this:
<% form_for :category, :url => { :action => "show" } do |f| %>
<%= select_tag :id, options_from_collection_for_select(Category.find(:all), :id, :name),
{ :onchange => "this.form.submit();"} %>
<% end %>
That will call a traditional html call, so it will refresh the entire page (and respond to format.html).
Then the controller will find the category by the submitted [:id]
@category = Category.find(params[:id])