.scrollTop()
may work:
$('select').scrollTop(30);
And you can scroll to a particular element using this:
var $s = $('select');
var optionTop = $s.find('[value="3"]').offset().top;
var selectTop = $s.offset().top;
$s.scrollTop($s.scrollTop() + (optionTop - selectTop));
Try it here: http://jsfiddle.net/kj9p4/
Note: does not work in Chrome.