http://harvesthq.github.io/chosen/
<link rel="stylesheet" type="text/css" href="engine/skins/chosen/chosen.css"/>
<script type="text/javascript" src="engine/skins/chosen/chosen.js"></script>
<script type="text/javascript">
$(function(){
$('#category').chosen({allow_single_deselect:true, no_results_text: 'No Category Selected'});
});
</script>
<link rel="stylesheet" type="text/css" href="{THEME}/js/chosen/chosen.css"/>
<script type="text/javascript" src="{THEME}/js/chosen/chosen.js"></script>
<script type="text/javascript">
$(function(){
$('#category').chosen({allow_single_deselect:true, no_results_text: 'No category found'});
});
</script>