<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script src="jquery.remoteselectoptions.min.js"></script>
<script>
$(function(){
$('select[name=countries]').remoteselectoptions({
url:'countries.html'
});
});
</script>
</head>
<body>
<em>select a country</em>
<select name="countries"><option value="IRL">Ireland</option></select>
<h3>source code</h3>
etc...
</body>
</html>
If you've any questions, please email me.