<script src="http://code.jquery.com/jquery-latest.js" type="text/javascript"></script>
<script>
$(function() {
$("#show").click(function() {
$("#more").toggle('slow');
return false;
});
});
</script>
<form>
<input name="one"/>
<a href="#" id="show">Покажи още инпутове</a>
<div id="more">
<input name="onemore"/>
</div>
</form>