Tab Mover от Guido Berhörster

Tab Mover is a Firefox Addon for quickly moving tabs between windows via the context menu. It can move tabs between two normal windows, two windows in incognito mode and from a normal window to an window in incognito mode. Since it is not possible to directly move a tab from a window in incognito mode to a normal window, Tab Mover can optionally close such a tab and reopen its URL in a normal window.