Say I have the following:
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
</ul>
<ul>
<li>First item</li>
<li class="something">Second item</li>
<li class="something">Third item</li>
</ul>
You should be able to use the "not" and "first child" selectors, like this:
$("li:not(:first-child)").addClass("something");