<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js"></script>
<select id="select1">
<option>1</option>
<option>2</option>
</select>
<div id="form"></div>
<script>
$('#select1').change(function(){
$('#form').append('<input type="button" id="post_btn" value="Добавить Пост">');
$('#post_btn').click(function(){
alert('есть!')
})
})
</script>