Da fällt mir in erster Linie FEBE ein, muss aber manuell gemacht werden:
https://addons.mozilla.org/de/firefox/addon/2109
ZitatFEBE allows you to quickly and easily backup your Firefox extensions. In fact, it goes beyond just backing up -- It will actually rebuild your extensions individually into installable .xpi files. Now you can easily synchronize your office and home browsers.