I have noticed that nowadays many websites use ajax to show enlarged images. When you click on an image, instead of the image opening in a new browser window, it opens using animation and zoom. This can be used to view multiple images on a website like a gallery.

Started searching for this. I did know about lightbox javascript library. But the one that impressed me finally is called prettyPhoto. This is a lightbox clone using jQuery. jQuery is a very powerful javascript library that I am very familiar with. I love this because of its simpilcity and because of all the plugins available to extend this.

Here is the link to the prettyPhoto library.
http://www.no-margin-for-errors.com/projects/prettyPhoto/

It is very simple to add to your website. You can see this working on my website below: (Try clicking an image on the website)
http://macpup.org/