Allows you to quickly change and apply a different locale from the
tools menu:
* Handy tool for all people involved with multilingual usage of Mozilla
  applications.
* Switches the Mozilla User Interface language (general.useragent.locale
  preference)
* Switches the accept_language preference, so complete websites will be
  translated. (if the http accept language header is supported, e.g.
  like Google does)
* Switches the Spell Checker Dictionary preference. (if supported by
  your Mozilla application)
* Remembers the dictionary and content locale for each site and
  automatically switches when you load that site. It also tries to detect
  the language of sites itself, and if found automatically switches to
  that language.
* Auto restarts the application in versions 1.4+ (only if needed)
* Includes country flag icons for 'all' countries by famfamfam.com.
* Displays the flag of the currently selected locale on your statusbar.
* Add 3 of your own custom defined locales.

WWW: http://www.captaincaveman.nl/?id=firefox_extensions