Fonts Ninja - Try fonts discovered on websites in any design software
Imagus - The extension is intended to complement image features that (I think) is missing from Opera by...
Adobe Capture - Turn any photo into a color theme, Look, vector graphic, or unique brush that you can use in your creative projects with Adobe Capture.
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
What Font Is - Find any font from any image (commercial or free)
Thumbnail Zoom Plus - The official site of the Thumbnail Zoom Plus add-on for Firefox