Hover Zoom - Enlarge thumbnails on mouse over.
Uforio - Uforio is an alternative client for Reddit.
Imagus - The extension is intended to complement image features that (I think) is missing from Opera by...
narwhal - Narwhal is a simple iOS app for reddit.
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
RedReader - RedReader - An unofficial open source Reddit client for Android.