How to make an explorer tree out of a list of links
<p>I have a list of topic categories that looks something like this mockup: <a href="http://www.problemio.com/problems/categories.php" rel="nofollow">http://www.problemio.com/problems/categories.php</a></p>

<p>And what I am trying to do is make each item clickable and expandable into the items that would match up.</p>

<p>I googled for such a thing and found only such things for file trees.  Is there a way to pull this off for the kind of list that I have?</p>

<p>Thanks!!</p>
