The Autocomplete widgets provides suggestions while you type into the field.

<script>
  $(document).ready(function() {
    var tags = ["ask","always", "all", "alright", "one", "foo", "blackberry", "tweet","force9", "westerners", "sport"];
    $( "#tags" ).autocomplete({
      source: tags
    });
  });
</script>
<input type='text' title='Tags' id='tags' />