You can't (to my knowledge) control the number of items displayed when the menu drops-down.
Everything else, is doable.
Code:
<html>
<head>
<title>Test</title>
<script type="text/javascript">
function jumpMenu( sel )
{
var val = sel.options[sel.selectedIndex].value;
if ( val != "" )
{
top.frames['body'].location.href = val;
}
}
</script>
</script>
</head>
<body>
<select onchange="jumpMenu( this )">
<option value="">Choose one</option>
<option value="http://www.google.com">Google</option>
<option value="http://www.yahoo.com">Yahoo</option>
<option value="http://www.lycos.com">Lycos</option>
</select>
<iframe name="body" width"=500" height"300"></iframe>
</body>
</html>