Hover Zoom is a Google Chrome extension that automatically shows full size view of images on hovering mouse over image thumbnails.
If the full size image is larger than your window then it is automatically resized to fit.
It can be configured to show zoomed images only when a keys is pressed. Pop-ups can be delayed and hover zoom can also be completely disabled for specific sites through the options.
Hover Zoom works on any site with direct links to image files. Ex. Amazon, deviantART, Facebook, Flickr, Google, Picasa Web Albums, etc.
Download: Hover Zoom