Prev/Next is a Firefox extension which creates two menu items in the Window menu for switching to the next/previous tab. This makes it possible to set the Keyboard Shortcut in Mac OS X through System Preferences.
Install the newest version from addons.mozilla.org.
Callout supports Firefox 3.0+.
Author: László Bácsi
Copyright (c) 2008-2009 László Bácsi, released under the Mozilla Public License Version 1.1 (or alternatively GPL 2.0 or LGPL 2.1).