Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Imagus - The extension is intended to complement image features that (I think) is missing from Opera by...
Snagit - Screen Capture Software for Windows and Mac
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
MWSnap - MWSnap is basically a free to use Windows snapping tools that are used for snapping any part of the screen that is currently displaying on the front of all opened programs and windows.
Thumbnail Zoom Plus - The official site of the Thumbnail Zoom Plus add-on for Firefox