<!-- HTML -->
<input type="text" id="input-text-4" size="40"/>
<ul id="values">
    <li>Smashing Magazine</li>
    <li>Woork Up</li>
    <li>Mashable</li>
</ul>

//JavaScript
$("ul[id='values'] li").click(function suggestValues(){
    input = $("input[id='input-text-4']");
    el = $(this).html();
      $(this).remove();
    newinput = input.val();
    newinput = (newinput + el + ", ");
    input.val(newinput);
  });

http://woorkup.com/2009/10/14/jquery-lessons-how-to-interact-with-html-forms/

Pick values from a list

list

jQuery