I just installed the Reveal Firefox extension. After the sweet interactive tutorial that comes with it, I must say this is a great extension. It has an interactive thumbnail tab bar that can be brought up just with one key stroke, which comes with a search thumbnail function as well. You can choose to search by URL, page or title. It also has a magnifying glass for does of you hard on seeing or just to take a better look at an image. Another great feature is the thumbnail previews on your back and forward buttons. That is not all it can do, there is a lot more so check it out: http://aluminum.sourmilk.net/reveal/
A must have extension for the hardcore Firefox user.