Ahmed Farooq saw my posts about Ligthbox and ThickBox image displaying solutions and send me an email that he develops something similar which is definitely worth mentioning.

iBox weights just 11 kb and supports image displaying and various other types of content, like HTML code. It has got a few useful configuration options that you can embed directly into the links. One big advantage is that the script is self-contained, so it would not conflict with other libraries you might include.

So if you want to say goodbye to the old school JavaScript pop-up windows, you have plenty of alternatives to choose from. Lightbox started it all, ThickBox is my personal favorite and iBox has the potential to outrun them both. Try them all and choose one that best suits your project.

Update (May 2015): Links removed, as they no longer work 🙁