$('li').addSingleClass('active')

This very small and basic jQuery Plugin adds a class to an element and removes this class from its siblings.

Why?

e.g.

$('#menu a').click(function(e) {
	e.preventDefault();
	$(this).addSingleClass('active');
});

So your click an a element it get the class active. If another sibling a had has this class it will be removed.

<div id="menu">
	<a href="#">Home</a>
	<a href="#">About</a>
	<a href="#" class="active">Contact</a>
</div>

Extended

Its also possible to perform more difficulte tasks. E.g. for manipulating the twitter bootstrap icons in your links:

$('#menu a').click(function(e) {
	e.preventDefault();
	$(this).addSingleClass({
		activeClass: 'active',
		activate: function() {
			$(this).find('i').addClass('icon-white');
		},
		inactivate: function() {
			$(this).find('i').removeClass('icon-white');
		}
	});
});

As you see, this will referer to the accordingly element.

Thats it!