<div id="dropdown"> 
  <p>请选择城市</p> 
  <ul> 
    <li><a href="#">长沙</a></li> 
    <li><a href="#">北京</a></li> 
    <li><a href="#">南京</a></li> 
    <li><a href="#">堪培拉</a></li> 
    <li><a href="#">多伦多</a></li> 
  </ul> 
</div> 

#dropdown{width:186px; margin:80px auto; position:relative} 
#dropdown p{width:150px; height:24px; line-height:24px; padding-left:4px; padding-right:30px; 
border:1px solid #a9c9e2; background:#e8f5fe url(arrow.gif) no-repeat right 4px; 
color:#807a62; cursor:pointer} 
#dropdown ul{width:184px; background:#e8f5fe; margin-top:2px; border:1px solid #a9c9e2; 
position:absolute; display:none} 
#dropdown ul li{height:24px; line-height:24px; text-indent:10px} 
#dropdown ul li a{display:block; height:24px; color:#807a62; text-decoration:none} 
#dropdown ul li a:hover{background:#c6dbfc; color:#369} 

$("#dropdown p").click(function(){ 
  var ul = $("#dropdown ul"); 
  if(ul.css("display")=="none"){ 
    ul.slideDown("fast"); 
  }else{ 
    ul.slideUp("fast"); 
  } 
}); 

$("#dropdown ul li a").click(function(){ 
  var txt = $(this).text(); 
  $("#dropdown p").html(txt); 
  $("#dropdown ul").hide(); 
}); 

<div id="dropdown"> 
  <p>请选择城市</p> 
  <ul> 
    <li><a href="#" rel="1">长沙</a></li> 
    <li><a href="#" rel="2">北京</a></li> 
    <li><a href="#" rel="3">南京</a></li> 
    <li><a href="#" rel="4">堪培拉</a></li> 
    <li><a href="#" rel="5">多伦多</a></li> 
  </ul> 
</div> 
<div id="result"></div> 

$("#dropdown ul li a").click(function(){ 
  var txt = $(this).text(); 
  $("#dropdown p").html(txt); 
  var value = $(this).attr("rel"); 
  $("#dropdown ul").hide(); 
  $("#result").html("您选择了"+txt+"，值为："+value); 
});