We have developed an extension called LocalisationUpdate. What it does is
load those localisations that are an exact match between the message on your
system and the message on SVN in English.
In theory it can be made to work for older releases, in practice it will
work from release 1.15 onwards. I have been testing it for some time now and
it works for me, what we want to know is that it works for you.
We are looking for people who run a MediaWiki Wiki and are willing to
upgrade to release 1.15 and test LocalisationUpdate in their environment. We
will support the first five wikis for five different languages that are
currently not fully localised. Obviously, in order to test it, you will
have to do some work at translatewiki.net