SO jQuery Fiddle
Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
<div id="selected">
<ul>
<li>29</li>
<li>16</li>
<li>5</li>
<li>8</li>
<li>10</li>
<li>7</li>
</ul>
</div>
JavaScript
var count = $("#selected li").length;
alert(count);
var count2 = $("#selected ul").children().length;
alert(count2);