This should do the trick for you.
var length = $('ul li').length;
while (length--) $('ul').append($('ul li')[length]);
Here is a working jsfiddle
You can use ajax sortable jquery plugin. One of my recommendation tutorial is Sortable Lists Using jQuery UI . Here user can re-order list using cursor pointer.
No jQuery solution :
var list = document.getElementsByTagName('ul')[0],
items = list.getElementsByTagName('li'),
i = items.length;
while (i--) list.appendChild(items[i]);
Here is a demo : http://jsfiddle.net/wared/tJaJ9/.
Based on cookie monster's suggestion :
var list = document.getElementsByTagName('ul')[0],
i = list.children.length;
while (i--) list.appendChild(list.children[i]);
Just for fun :
var list = document.getElementsByTagName('ul')[0],
items = Array.prototype.slice.call(list.children);
while (items.length) list.appendChild(items.pop());
A jQuery one :
$('ul').append($('li').get().reverse());