Brings Emacs' iswitchb-mode to Firefox. Lets you easily switch between tabs by just typing part of the tab title. Great if you keep a lot of tabs open in many different windows, or if you just want to conveniently switch tabs using only a few keystrokes.
Just press F9, or find it in the Tools menu, and a window that lists all your tabs (in every browser window) appears. Start typing part of a tab name, and the list will narrow down. Use the up and down keys to find the tab you want and hit enter. That tab will be selected, and the browser window the tab is in will be brought to the front.
See the website for more details. The keyboard shortcut will be made configurable in an upcoming release.
iswitchb-tabs is open-source under the MPL/GPL/LGPL tri-license. See the project webpage for access to the Subversion respository.