Reddit-Hover-Craft is a project mainly written in JavaScript, it's free.
This will open a jQuery popup dialog displaying images when you hover over img links on Reddit
I got sick of clicking on links to view images that were posted to Reddit.com so I wrote this Google Chrome extension that will display the image in a popup dialog when you hover over the image link.
Install Google Chrome go here to install it.
https://chrome.google.com/extensions/detail/ilfijghjjdfgnblnkemkhknmdphchnmk?hl=en