콤보 박스에 머가 들었는지 클릭하지 않더라도 돌려가면서 보는 방법을 즉흥적으로 만들었네요.
역시 고수가 많다는것을 새삼 느낍니다.

<form name="qform">
<select name="qsel" onfocus="stop_roll();" onmouseover="stop_roll();" onclick="flag_expand = 'Y';" onblur="flag_expand = 'N'; start_roll();" onmouseout="start_roll();" onchange="eval(this.value); this.blur();">
<option>-선 택-</option>
<option value="window.open('http://www.empas.com/');">엠파스</option>
<option value="window.open('http://www.naver.com/');">네이버</option>
<option value="window.open('http://www.daum.net/');">다음</option>
<option value="alert('My name is Lain. ^-^ㆀ'); alert('Nice to meet you!');">Who are you?</option>
<option value="document.body.style.background = '#AAAAAA';">배경색 바꾸기</option>
<option value="document.body.style.background = '';">배경색 원래대로</option>
</select>
</form>

<script language="javascript">
<!--
var obj = document.qform.qsel, flag_expand = 'N', cnt = 1, timer;

function start_roll(){
if(flag_expand == 'N'){
if(cnt >= obj.length) cnt = 1;
obj.options[cnt].selected = true;
cnt++;
timer=setTimeout('start_roll()', 1000);
}
}

function stop_roll(){
obj.options[0].selected = true;
clearTimeout(timer);
}

start_roll();
//-->
</script>