TabFlip

With TabFlip you are able to flip through your tabs with great ease. By right-click dragging on the page you will intuitively flip through your tabs getting a quick glimpse of whats in them.

Features:

Right-click drag on the page to flip through your tabs.
Right-click drag on the tab-bar to flip through your tabs by directly hovering over them.
Flip through tabs by scrolling horizontally. Great for track-pads that enable a two finger swipe or have a designated stroke for horizontal scrolling. (Disabled by default)

Options:

Enable wrapping so you jump to your first tab when reaching your last.
Customize the sensitivity at which you switch tabs.

Notice:
TabFlip modifies when the context-menu appears on Macs so it doesn't get in the way when flipping tabs. Instead of appearing upon pressing the mousebutton, the context-menu will appear upon releasing.

Support & Feedback:
https://forums.mozilla.org/addons/viewtopic.php?f=23&t=14965

-from the Mozilla add-on page.