link.haml

%a(href="#" toggles="#advanced_search, #simple_search") Advanced Search

linkToggle.js

var FS = FS || {};
FS.Toggler = Class.create({
  options: {
    trigger: 'a[toggles]'
  },
  initialize: function(options){
    this.options = $H(this.options).merge($H(options));
    var elements = $$(this.options.get('trigger'));
    elements.each(function(el){
      el.observe('click', function(event){event.stop(); this.click(el);}.bind(this));
      el.store('toggle-elements', this.getElementsFromString(el.readAttribute('toggles')));
    }.bind(this))
  },
  click: function(el){
    el.retrieve('toggle-elements').invoke('toggle');
  },
  getElementsFromString: function(elementString){
    return elementString.split(',').map(function(str){
      str = str.strip();
      return (str.include(".") || str.include(" ") ? $$(str) : $(str.replace('#', '')))
    }).flatten();
  }
});

document.observe("dom:loaded", function() {
  new FS.Toggler();
});