这个其实比较简单.确很实用
<form name="form1">
<select name="select1">
<option value="aa">aa</option>
<option value="bb">bb</option>
<option value="cc">cc</option>
</select>
</form>
<a href="javascript:window.location.href='aa.asp?id=' + document.form1.select1.value">点击</a>