A very lightweight and simple JS lightbox.
Simply load the required files:
<link href="/path/to/minLightBox.css" rel="stylesheet">
<script src="/path/to/minLightBox.js"></script>
and mark up your HTML:
<div>
<a href="slide-1.jpg" data-gallery="gallery-1"/>
<img src="slide-1.jpg"/>
</a>
<a href="slide-2.jpg" data-gallery="gallery-1"/>
<img src="slide-2.jpg"/>
</a>
<a href="slide-3.jpg" data-gallery="gallery-1"/>
<img src="slide-3.jpg"/>
</a>
</div>