Hover Zoom - Enlarge thumbnails on mouse over.
Uforio - Uforio is an alternative client for Reddit.
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
narwhal - Narwhal is a simple iOS app for reddit.
Hover Zoom+ - Google Chrome extension for zooming images on mouse hover - extesy/hoverzoom
RedReader - RedReader - An unofficial open source Reddit client for Android.